OPA890IDBV

Burr Brown Products from Texas Instruments OP A8 90 OPA890 SBOS369 – MAY 2007 Low-Power, Wideband, Voltage-Feedback OPERATIONAL AMPLIFIER with Disable FEATURES • FLEXIBLE SUPPLY RANGE: +3V to +12V Single Supply ±1.5V to ±6V Dual Supplies UNITY-GAIN STABLE WIDEBAND +5V OPERATION: 115MHz (G = +2V/V) OUTPUT VOLTAGE SWING: ±4V HIGH SLEW RATE: 500V/µs LOW QUIESCENT CURRENT: 1.1mA LOW DISABLE CURRENT: 30µA DESCRIPTION The OPA890 represents a major step forward in unity-gain stable, voltage-feedback op amps. A new internal architecture provides slew rate and full-power bandwidth previously found only in wideband, current-feedback op amps. These capabilities provide exceptional full power bandwidth. Using a single +5V supply, the OPA890 can deliver a 1V to 4V output swing with over 35mA drive current and 220MHz bandwidth. This combination of features makes the OPA890 an ideal RGB line driver or single-supply analog-to-digital converter (ADC) input driver. The low 1.1mA supply current of the OPA890 is precisely trimmed at +25°C. This trim, along with low temperature drift, ensures lower maximum supply current than competing products. System power may be reduced further using the optional disable control pin. Leaving this disable pin open, or holding it HIGH, operates the OPA890 normally. If pulled LOW, the OPA890 supply current drops to less than 30µA while the output goes into a high-impedance state. RELATED OPERATIONAL AMPLIFIER PRODUCTS DESCRIPTION Low-Power Voltage-Feedback with Disable SINGLES — OPA690 OPA691 OPA692 DUALS OPA2890 OPA2690 OPA2691 — TRIPLES — OPA3690 OPA3691 OPA3692 • • • • • • • • • • • • • APPLICATIONS VIDEO LINE DRIVING xDSL LINE DRIVERS/RECEIVERS HIGH-SPEED IMAGING CHANNELS ADC BUFFERS PORTABLE INSTRUMENTS TRANSIMPEDANCE AMPLIFIERS ACTIVE FILTERS Multiplying DAC Transimpedance Amplifier +5V DB0 DB1 VREF DB2 ½ DB3 R1 DAC7822 DB4 RFB DB5 DB6 IOUT1 DB7 IOUT2 DB8 DB9 R2 DB10 R2_3 DB11 R3 VDD GND -5V Voltage-Feedback Amplifier with Disable (1800V/µs) Current-Feedback Amplifier with Disable (2100V/µs) 2.5pF +7.5V Fixed Gain OPA890 VOUT 0V £ VOUT £ 5V 5.56kW 0.1mF -2.5V Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. All trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 2007, Texas Instruments Incorporated OPA890 www.ti.com SBOS369 – MAY 2007 This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. ORDERING INFORMATION (1) PACKAGE DESIGNATOR D DBV SPECIFIED TEMPERATURE RANGE –40°C to +85°C –40°C to +85°C PACKAGE MARKING OPA890 BRI ORDERING NUMBER OPA890ID OPA890IDR OPA890IDBVT OPA890IDBVR TRANSPORT MEDIA, QUANTITY Rail, 75 Tape and Reel, 2500 Tape and Reel, 250 Tape and Reel, 3000 PRODUCT OPA890 OPA890 (1) PACKAGE-LEAD SO-8 SOT23-6 For the most current package and ordering information see the Package Option Addendum at the end of this document, or see the TI web site at www.ti.com. ABSOLUTE MAXIMUM RATINGS (1) Over operating free-air temperature range (unless otherwise noted). OPA890 Power Supply Internal Power Dissipation Input Voltage Range Storage Temperature Range Lead Temperature (soldering, 10s) Maximum Junction Temperature (TJ) Maximum Junction Temperature, Continuous Operation, Long-Term Reliability Human Body Model (HBM) ESD Rating: Charge Device Model (CDM) Machine Model (MM) (1) ±6.5 ±VS –40 to +125 +260 +150 +140 2000 1500 200 UNIT V V °C °C °C °C V V V See Thermal Characteristics Stresses above these ratings may cause permanent damage. Exposure to absolute maximum conditions for extended periods may degrade device reliability. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those specified is not implied. PIN CONFIGURATIONS TOP VIEW SO TOP VIEW Output -VS NC Inverting Input Noninverting Input -VS 1 2 3 4 8 7 6 5 DIS +VS Output NC 6 5 4 Noninverting Input 1 2 3 6 5 4 +VS DIS Inverting Input SOT23 BRI 1 2 3 Pin Orientation/Package Marking NC = No Connection 2 Submit Documentation Feedback OPA890 www.ti.com SBOS369 – MAY 2007 ELECTRICAL CHARACTERISTICS: VS = ±5V Boldface limits are tested at +25°C. At RF = 750Ω, G = +2V/V, and RL = 100Ω, unless otherwise noted. OPA890ID, IDBV TYP PARAMETER AC PERFORMANCE Small-Signal Bandwidth G = +1V/V, VO = 100mVPP, RF = 0Ω G = +2V/V, VO = 100mVPP G = +10V/V, VO = 100mVPP Gain Bandwidth Product Bandwidth for 0.1dB Flatness Peaking at a Gain of +1V/V Large-Signal Bandwidth Slew Rate Rise-and-Fall Time Settling Time to 0.02% Settling Time to 0.1% Harmonic Distortion 2nd-Harmonic G = +2V/V, f = 1MHz, VO = 2VPP RL = 200Ω RL ≥ 500Ω 3rd-Harmonic RL = 200Ω RL ≥ 500Ω Input Voltage Noise Input Current Noise Differential Gain Differential Phase Channel-to-Channel Crosstalk DC PERFORMANCE (4) Open-Loop Voltage Gain (AOL) Input Offset Voltage Average Offset Voltage Drift Input Bias Current Average Input Bias Current Drift Input Offset Current Average Input Offset Current Drift INPUT Common-Mode Input Range (CMIR) (5) Common-Mode Rejection Ratio (CMRR) Input Impedance Differential Common-Mode OUTPUT Output Voltage Swing No Load RL = 100Ω Output Current, Sourcing, Sinking Peak Output Current Closed-Loop Output Impedance VO = 0V Output Shorted to Ground G = +2V/V, f = 100kHz ±4.0 ±3.5 ±40 ±75 0.04 ±3.9 ±3.1 ±35 ±3.8 ±3.05 ±33 ±3.7 ±2.9 ±30 V V mA mA Ω min min min typ typ A A A C C VCM = 0V VCM = 0V 190 || 0.6 3.2 || 0.9 kΩ || pF MΩ || pF typ typ C C VCM = 0V, Input-Referred ±3.9 67 ±3.8 61 ±3.7 58 ±3.6 57 V dB min min A A VO = 0V, RL = 100Ω VCM = 0V VCM = 0V VCM = 0V VCM = 0V VCM = 0V VCM = 0V ±70 ±350 ±0.1 ±1.6 62 ±1 57 ±5 56 ±5.7 ±15 ±1.8 ±5 ±450 ±2.5 54 ±6 ±15 ±2 ±6 ±500 ±2.5 dB mV µV/°C µA nA/°C nA nA/°C min max max max max max max A A B A B A B f > 100kHz f > 100kHz G = +2V/V, VO = 1.4VPP, RL = 150Ω G = +2V/V, VO = 1.4VPP, RL = 150Ω f = 5MHz, Input-Referred -88 -102 -89 -94 8 1 0.05 0.03 –68 -78 -84 -84 -90 9 1.3 -76 -82 -81 -87 10 1.7 -75 -80 -80 -86 11 1.9 dBc dBc dBc dBc nV/√Hz pA/√Hz % ° dB max max max max max max typ typ typ B B B B B B C C C G > +20V/V G = +2V/V, VO = 100mVPP VO < 100mVPP G = +2V/V, VO = 2VPP G = +2V/V, VO = 2V Step 0.2V Step G = +1V/V, VO = 2V Step 260 115 13 130 20 1 170 500 3.5 16 10 325 300 275 75 9 100 65 8 90 60 7.5 85 MHz MHz MHz MHz MHz dB MHz V/µs ns ns ns typ min min min typ typ typ min typ typ typ C B B B C C C B C C C CONDITIONS +25°C MIN/MAX OVER TEMPERATURE +25°C (2) 0°C to +70°C (3) –40°C to +85°C (3) UNITS MIN/ MAX TEST LEVEL (1) (1) (2) (3) (4) (5) Test levels: (A) 100% tested at +25°C. Over temperature limits set by characterization and simulation. (B) Limits set by characterization and simulation. (C) Typical value only for information. Junction temperature = ambient for +25°C tested specifications. Junction temperature = ambient at low temperature limit; junction temperature = ambient +2°C at high temperature limit for over temperature specifications. Current is considered positive out-of-node. VCM is the input common-mode voltage. Tested < 3dB below minimum specified CMRR at ±CMIR limits Submit Documentation Feedback 3 OPA890 www.ti.com SBOS369 – MAY 2007 ELECTRICAL CHARACTERISTICS: VS = ±5V (continued) Boldface limits are tested at +25°C. At RF = 750Ω, G = +2V/V, and RL = 100Ω, unless otherwise noted. OPA890ID, IDBV TYP PARAMETER DISABLE Power-Down Supply Current (+VS) Disable Time Enable Time Off Isolation Output Capacitance in Disable Enable Voltage Disable Voltage Control Pin Input Bias Current (VDIS) POWER SUPPLY Specified Operating Voltage Minimum Operating Voltage Maximum Operating Voltage Maximum Quiescent Current Minimum Quiescent Current Power-Supply Rejection Ratio (+PSRR) VS = ±5V VS = ±5V +VS = 4.5V to 5.5V 1.1 1.1 74 ±5 ±1.5 ±6.0 1.2 1.05 66 ±6.0 1.22 1.02 62 ±6.0 1.25 1 60 V V V mA mA dB typ typ max max min min C C A A A A VDIS = 0V, Each Channel CONDITIONS Disable LOW VDIS = 0 VIN = 1VDC VIN = 1VDC G = +2V/V, f = 5MHz 30 7 200 70 4 3.0 1.4 15 3.2 1.1 30 3.4 1.0 35 3.8 0.8 40 55 60 75 µA µs ns dB pF V V µA max typ typ typ typ min max max A C C C C A A A +25°C MIN/MAX OVER TEMPERATURE +25°C (2) 0°C to +70°C (3) –40°C to +85°C (3) UNITS MIN/ MAX TEST LEVEL (1) THERMAL CHARACTERISTICS Specified Operating Range Thermal Resistance θJA D DBV SO-8 SOT23-6 Junction-to-Ambient 105 110 °C/W °C/W typ typ C C –40 to +85 °C typ C 4 Submit Documentation Feedback OPA890 www.ti.com SBOS369 – MAY 2007 ELECTRICAL CHARACTERISTICS: VS = +5V Boldface limits are tested at +25°C. At RF = 750Ω, G = +2V/V, and RL = 100Ω, unless otherwise noted. OPA890ID, IDBV TYP PARAMETER AC PERFORMANCE Small-Signal Bandwidth G = +1V/V, VO = 100mVPP, RF = 0Ω G = +2V/V, VO = 100mVPP G = +10V/V, VO = 100mVPP Gain Bandwidth Product Bandwidth for 0.1dB Flatness Peaking at a Gain of +1V/V Large-Signal Bandwidth Slew Rate Rise-and-Fall Time Settling Time to 0.02% Settling Time to 0.1% Harmonic Distortion 2nd-Harmonic G = +2V/V, f = 1MHz, VO = 2VPP RL = 200Ω RL ≥ 500Ω 3rd-Harmonic RL = 200Ω RL ≥ 500Ω Input Voltage Noise Input Current Noise Differential Gain Differential Phase Channel-to-Channel Crosstalk DC PERFORMANCE (4) Open-Loop Voltage Gain (AOL) Input Offset Voltage Average Offset Voltage Drift Input Bias Current Average Input Bias Current Drift Input Offset Current Average Input Offset Current Drift INPUT Most Positive Input Voltage (5) Least Positive Input Voltage (5) Common-Mode Rejection Ratio (CMRR) Input Impedance Differential Common-Mode OUTPUT Most Positive Output Voltage No Load RL = 100Ω Least Positive Output Voltage No Load RL = 100Ω Output Current: Sourcing, Sinking Short-Circuit Output Current Closed-Loop Output Impedance VO = VS/2 Output Shorted to Ground G = +2V/V, f = 100kHz +4.0 +3.9 +1.0 +1.1 ±35 ±65 0.04 +3.9 +3.75 +1.1 +1.35 ±30 +3.85 +3.7 +1.15 +1.4 ±28 +3.8 +3.65 +1.2 +1.45 ±25 V V V V mA mA Ω min min max max min typ typ A A A A A C C VCM = VS/2 VCM = VS/2 190 || 0.6 3.2 || 0.9 kΩ || pF MΩ || pF typ typ C C VCM = VS/2, Input-Referred +4 +1 65 +3.8 +1.2 59 +3.75 +1.2 56 +3.7 +1.3 55 V V dB min max min A A A VO = VS/2, RL = 100Ω VCM = VS/2 VCM = VS/2 VCM = VS/2 VCM = VS/2 VCM = VS/2 VCM = VS/2 ±70 ±400 ±0.1 ±1.7 60 ±1 55 ±5 54 ±5.7 ±15 ±1.9 ±5 ±500 ±2.5 52 ±6 ±15 ±2.1 ±6 ±550 ±2.5 dB mV µV/°C µA nA/°C nA nA/°C min max max max max max max A A B A B A B f > 100kHz f > 100kHz G = +2V/V, VO = 1.4VPP, RL = 150Ω G = +2V/V, VO = 1.4VPP, RL = 150Ω f = 5MHz, Input-Referred -85 -90 -85 -87 8.1 1.1 0.06 0.04 -68 -76 -78 -81 -84 9.1 1.4 -73 -74 -79 -82 10.1 1.7 -72 -73 -78 -81 11.1 2.0 dBc dBc dBc dBc nV/√Hz pA/√Hz % ° dB max max max max max max typ typ typ B B B B B B C C C G > +20V/V G = +2V/V, VO = 100mVPP VO < 100mVPP G = +2V/V, VO = 2VPP G = +2V/V, VO = 2V Step 0.2V Step G = +1V/V, VO = 2V Step 220 105 12 125 16 2 130 350 3.8 18 12 250 200 175 70 8 90 60 6.8 75 55 6.3 70 MHz MHz MHz MHz MHz dB MHz V/µs ns ns ns typ min min min typ typ typ min typ typ typ C B B B C C C B C C C CONDITIONS +25°C MIN/MAX OVER TEMPERATURE +25°C (2) 0°C to +70°C (3) –40°C to +85°C (3) UNITS MIN/ MAX TEST LEVEL (1) (1) (2) (3) (4) (5) Test levels: (A) 100% tested at +25°C. Over temperature limits set by characterization and simulation. (B) Limits set by characterization and simulation. (C) Typical value only for information. Junction temperature = ambient for +25°C tested specifications. Junction temperature = ambient at low temperature limit; junction temperature = ambient +2°C at high temperature limit for over temperature specifications. Current is considered positive out-of-node. VCM is the input common-mode voltage. Tested < 3dB below minimum specified CMRR at ±CMIR limits Submit Documentation Feedback 5 OPA890 www.ti.com SBOS369 – MAY 2007 ELECTRICAL CHARACTERISTICS: VS = +5V (continued) Boldface limits are tested at +25°C. At RF = 750Ω, G = +2V/V, and RL = 100Ω, unless otherwise noted. OPA890ID, IDBV TYP PARAMETER DISABLE Power-Down Supply Current (+VS) Disable Time Enable Time Off Isolation Output Capacitance in Disable Enable Voltage Disable Voltage Control Pin Input Bias Current (VDIS) POWER SUPPLY Specified Operating Voltage Minimum Operating Voltage Maximum Operating Voltage Maximum Quiescent Current Minimum Quiescent Current Power-Supply Rejection Ratio THERMAL CHARACTERISTICS Specified Operating Range Thermal Resistance θJA D DBV SO-8 SOT23-6 Junction-to-Ambient 105 110 °C/W °C/W typ typ C C –40 to +85 °C typ C (+PSRR) VS = +5V VS = +5V +VS = 4.5V to 5.5V 1.06 1.06 65 +5 +3 +12 1.18 0.92 +12 1.20 0.90 +12 1.25 0.87 V V V mA mA dB typ typ max max min typ C C A A A C VDIS = 0V, Each Channel CONDITIONS Disable LOW VDIS = 0V, both channels VOUT = 1VDC VOUT = 1VDC G = +2V/V, f = 5MHz 18 7 200 70 4 3.0 1.4 15 3.2 1.1 30 3.4 1.0 35 3.8 0.8 40 45 50 65 µA ns ns dB pF V V µA max typ typ typ typ min max max A C C C C A A A +25°C MIN/MAX OVER TEMPERATURE +25°C (2) 0°C to +70°C (3) –40°C to +85°C (3) UNITS MIN/ MAX TEST LEVEL (1) 6 Submit Documentation Feedback OPA890 www.ti.com SBOS369 – MAY 2007 TYPICAL CHARACTERISTICS: VS = ±5V At TA = +25°C, G = +2V/V, RF = 750Ω, and RL = 200Ω, unless otherwise noted. SMALL-SIGNAL FREQUENCY RESPONSE 3 0 G = +1V/V R F = 0W 9 6 3 1VPP 2VPP LARGE-SIGNAL FREQUENCY RESPONSE Normalized Gain (dB) -3 -6 -9 -12 -15 VO = 0.1VPP -18 1 10 Frequency (MHz) G = +2V/V G = +5V/V G = +10V/V 100 600 Gain (dB) 0 4VPP -3 7VPP -6 -9 1 RL = 200W G = +2V/V 10 Frequency (MHz) 100 400 Figure 1. SMALL-SIGNAL PULSE RESPONSE 400 300 VO = 0.5VPP G = +2V/V 3 2 VO = 5VPP G = +2V/V Figure 2. LARGE-SIGNAL PULSE RESPONSE Output Voltage (mV) Output Voltage (V) Time (10ns/div) 200 100 0 -100 -200 -300 -400 1 0 -1 -2 -3 Time (10ns/div) Figure 3. VIDEO DIFFERENTIAL GAIN/DIFFERENTIAL PHASE 0.20 0.18 0.16 -dP -dG 0.40 0.36 Figure 4. DISABLE FEEDTHROUGH -45 -50 VDIS = 0V Input Referred Disable Feedthrough (dB) 0.32 0.28 0.24 +dG +dP 0.20 0.16 0.12 0.08 0.04 0 1 2 3 Number of 150W Loads 4 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0 Differential Phase (°) Differential Gain (%) -55 -60 -65 -70 -75 -80 -85 -90 1 10 Frequency (MHz) 100 Figure 5. Figure 6. Submit Documentation Feedback 7 OPA890 www.ti.com SBOS369 – MAY 2007 TYPICAL CHARACTERISTICS: VS = ±5V (continued) At TA = +25°C, G = +2V/V, RF = 750Ω, and RL = 200Ω, unless otherwise noted. HARMONIC DISTORTION vs LOAD RESISTANCE -80 -85 3rd Harmonic -90 -95 2nd Harmonic -100 -105 -110 100 Load Resistance (W) 1k VO = 2VPP f = 1MHz G = +2V/V 1MHz HARMONIC DISTORTION vs SUPPLY VOLTAGE -80 VO = 2VPP RL = 200W G = +2V/V 3rd Harmonic -90 2nd Harmonic -95 Harmonic Distortion (dBc) Harmonic Distortion (dBc) -85 -100 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 Supply Voltage (±VS) Figure 7. HARMONIC DISTORTION vs FREQUENCY -50 -60 -70 3rd Harmonic -80 -90 2nd Harmonic -100 -110 0.1 1 Frequency (MHz) 10 -70 VO = 2VPP RL = 200W G = +2V/V -75 -80 Figure 8. HARMONIC DISTORTION vs OUTPUT VOLTAGE RL = 200W f = 1MHz G = +2V/V Harmonic Distortion (dBc) Harmonic Distortion (dBc) 3rd Harmonic -85 -90 -95 2nd Harmonic -100 0.1 1 Output Voltage Swing (VPP) 10 Figure 9. HARMONIC DISTORTION vs NONINVERTING GAIN -70 -75 VO = 2VPP RL = 200W f = 1MHz -70 Figure 10. HARMONIC DISTORTION vs INVERTING GAIN VO = 2VPP RL = 200W f = 1MHz 3rd Harmonic Harmonic Distortion (dBc) -80 -85 -90 -95 -100 -105 1 3rd Harmonic Harmonic Distortion (dBc) -75 2nd Harmonic 2nd Harmonic -80 -85 -90 10 Gain (V/V) 20 -1 Gain (V/V) -10 -20 Figure 11. Figure 12. 8 Submit Documentation Feedback OPA890 www.ti.com SBOS369 – MAY 2007 TYPICAL CHARACTERISTICS: VS = ±5V (continued) At TA = +25°C, G = +2V/V, RF = 750Ω, and RL = 200Ω, unless otherwise noted. LOW-FREQUENCY INVERTING HARMONIC DISTORTION -90 -95 -100 2nd Harmonic -105 -110 3rd Harmonic -115 -120 1k 10k 100k Frequency (Hz) 1M VO = 2VPP RL = 500W G = -1V/V TWO-TONE, 3RD-ORDER INTERMODULATION SPURIOUS -40 Load Power at Matched 50W Load -50 10MHz 5MHz Harmonic Distortion (dBc) Spurious Point (dBc) -60 -70 -80 -90 1MHz -100 -110 -8 -6 -4 -2 0 2 4 6 8 Single-Tone Load Power (dBm) Figure 13. RECOMMENDED RS vs CAPACITIVE LOAD 100 9 G = +2V/V 6 Figure 14. FREQUENCY RESPONSE vs CAPACITIVE LOAD CL = 10pF RS (W) 3 Gain (dB) CL = 100pF 0 CL = 47pF -3 -6 VIN OPA890 CL 750W NOTE: (1) 1kW is optional. RS VOUT 1kW(1) CL = 22pF 10 750W 1 1 10 100 1000 Capacitive Load (pF) -9 0 20 40 60 80 100 120 140 160 180 200 Frequency (MHz) Figure 15. COMMON-MODE REJECTION RATIO AND POWER-SUPPLY REJECTION RATIO vs FREQUENCY 80 70 CMRR +PSRR 50 40 30 20 10 0 1k 10k 100k 1M 10M 100M Frequency (Hz) 100 -PSRR Figure 16. INPUT VOLTAGE AND CURRENT NOISE 60 Voltage Noise Density (nV/ÖHz) Current Noise Density (pA/ÖHz) CMRR and PSRR (dB) 10 Voltage Noise Density (8nV/ÖHz) 1 Current Noise Density (1pA/ÖHz) 0.1 10 100 1k 10k 100k 1M 10M Frequency (Hz) Figure 17. Figure 18. Submit Documentation Feedback 9 OPA890 www.ti.com SBOS369 – MAY 2007 TYPICAL CHARACTERISTICS: VS = ±5V (continued) At TA = +25°C, G = +2V/V, RF = 750Ω, and RL = 200Ω, unless otherwise noted. SUPPLY AND OUTPUT CURRENT vs TEMPERATURE 1.15 1.14 1.13 Supply Current Output Current, Sourcing 50 49 Input Offset Voltage (V) 2.10 Input Bias Current (IB) 2.05 200 150 100 50 0 Input Offset Voltage (VOS) -50 -100 -50 -25 0 25 50 75 100 125 Ambient Temperature (°C) TYPICAL DC DRIFT vs TEMPERATURE Input Bias and Input Offset Currents (nA) 250 48 47 46 45 44 Supply Current (mA) 1.12 1.11 1.10 1.09 1.08 1.07 1.06 1.05 -50 -25 0 25 50 Output Current,Sinking Output Current (mA) 2.00 1.95 1.90 1.85 1.80 1.75 Input Offset Current (IOS) 43 42 41 40 75 100 125 Ambient Temperature (°C) Figure 19. LARGE-SIGNAL DISABLE/ENABLE RESPONSE 6 8 4 2 0 4 -2 Figure 20. NONINVERTING OVERDRIVE RECOVERY 4 3 2 Output Voltage Left Scale Input Voltage Right Scale 1 0 -1 -3 -3 -4 Time (10ns/div) VDIS (V) 6 Output Voltage (V) 4 2 0 -2 -4 -6 -8 Output Voltage (V) 3 2 1 0 -1 Time (5ns/div) Figure 21. CLOSED-LOOP OUTPUT IMPEDANCE vs FREQUENCY 100 ZO Figure 22. OPEN-LOOP GAIN AND PHASE 80 70 Open-Loop Gain 180 160 Output Impedance (W) 10 Open-Loop Gain (dB) 324W OPA890 1 750W 50 40 30 20 10 0 Open-Loop Phase 120 100 80 60 40 20 0 100 1k 10k 100k 1M 10M 100M 1G Frequency (Hz) 0.1 750W 0.01 0.001 1k 10k 100k 1M 10M 100M Frequency (Hz) -10 Figure 23. Figure 24. 10 Submit Documentation Feedback Open-Loop Phase (°) 60 140 Input Voltage (V) OPA890 www.ti.com SBOS369 – MAY 2007 TYPICAL CHARACTERISTICS: VS = ±5V, Differential At TA = +25°C, Differential Gain = +2V/V, RF = 750Ω, and RL = 400Ω, unless otherwise noted. DIFFERENTIAL SMALL-SIGNAL FREQUENCY RESPONSE 3 GD = 1V/V 0 6 GD = 5VPP 3 DIFFERENTIAL LARGE-SIGNAL FREQUENCY RESPONSE 9 Normalized Gain (dB) -3 -6 -9 -12 -15 -18 1 RF = 750W RL = 400W 10 Frequency (MHz) 100 300 GD = 2V/V GD = 5V/V GD = 10V/V Gain (dB) 0 GD = 14VPP -3 -6 GD = 8VPP -9 1 10 Frequency (MHz) 100 300 Figure 25. DIFFERENTIAL DISTORTION vs LOAD RESISTANCE -70 -75 3rd Harmonic -30 -40 Figure 26. DIFFERENTIAL DISTORTION vs FREQUENCY RL = 400W GD = 2V/V Harmonic Distortion (dBc) Harmonic Distortion (dBc) -80 -85 -90 -95 -100 -105 -110 -115 -120 3rd Harmonic -50 -60 -70 -80 -90 -100 -110 -120 2nd Harmonic 2nd Harmonic VO = 4VPP f = 1MHz GD = 2V/V 100 Load Resistance (W) 1k 1 Frequency (MHz) 10 20 Figure 27. DIFFERENTIAL DISTORTION vs OUTPUT VOLTAGE -75 -80 RL = 400W f = 1MHz GD = 2V/V Figure 28. Harmonic Distortion (dBc) 3rd Harmonic -85 -90 -95 -100 2nd Harmonic -105 -110 0.1 1 Output Voltage (VPP) 10 Figure 29. Submit Documentation Feedback 11 OPA890 www.ti.com SBOS369 – MAY 2007 TYPICAL CHARACTERISTICS: VS = +5V At TA = +25°C, G = +2V/V, RF = 750Ω, and RL = 200Ω, unless otherwise noted. SMALL-SIGNAL FREQUENCY RESPONSE 3 0 G = +1V/V RF = 0W LARGE-SIGNAL FREQUENCY RESPONSE 9 6 1VPP 3 Normalized Gain (dB) -3 -6 -9 G = +2V/V -12 G = +5V/V -15 VO = 100mVPP -18 1 10 Frequency (MHz) 100 500 G = +10V/V Gain (dB) 0 2VPP -3 3VPP -6 -9 1 RL = 200W G = +2V/V 10 Frequency (MHz) 100 300 Figure 30. SMALL-SIGNAL PULSE RESPONSE 2.9 2.8 VO = 0.5VPP G = +2V/V 4.1 3.7 VO = 0.5VPP G = +2V/V Figure 31. LARGE-SIGNAL PULSE RESPONSE Output Voltage (V) 2.6 2.5 2.4 2.3 2.2 2.1 Time (10ns/div) Output Voltage (V) 2.7 3.3 2.9 2.5 2.1 1.7 1.3 0.9 Time (10ns/div) Figure 32. RECOMMENDED RS vs CAPACITIVE LOAD 200 100 9 Figure 33. FREQUENCY RESPONSE vs CAPACITIVE LOAD VIN OPA890 RS VOUT CL 750W NOTE: (1) 1kW is optional. 1kW(1) 6 3 750W Gain (dB) RS (W) 0 CL = 22pF -3 CL = 47pF -6 CL = 100pF 0 20 40 60 80 100 120 140 160 180 200 CL = 10pF 10 1 1 10 100 1000 Capacitive Load (pF) -9 Frequency (MHz) Figure 34. Figure 35. 12 Submit Documentation Feedback OPA890 www.ti.com SBOS369 – MAY 2007 TYPICAL CHARACTERISTICS: VS = +5V (continued) At TA = +25°C, G = +2V/V, RF = 750Ω, and RL = 200Ω, unless otherwise noted. NONINVERTING OVERDRIVE RECOVERY 6.5 5.5 4.5 4.0 -75 HARMONIC DISTORTION vs LOAD RESISTANCE VO = 2VPP f = 1MHz GD = +2V/V Harmonic Distortion (dBc) Output Voltage (1V/div) 3.5 2.5 1.5 0.5 -0.5 -1.5 Output Voltage Left Scale Input Voltage Right Scale 3.0 2.5 2.0 1.5 1.0 0.5 Time (10ns/div) Input Voltage (1V/div) 4.5 3.5 -80 -85 3rd Harmonic -90 2nd Harmonic -95 100 Load Resistance (W) 1k Figure 36. HARMONIC DISTORTION vs FREQUENCY -50 VO = 2VPP RL = 200W to VS/2 G = +2V/V 3rd Harmonic -45 Figure 37. HARMONIC DISTORTION vs OUTPUT VOLTAGE f = 1MHz G = +2V/V RL = 200W to VS/2 Harmonic Distortion (dBc) -60 Harmonic Distortion (dBc) -55 -70 2nd Harmonic -65 2nd Harmonic -80 -75 3rd Harmonic -90 -85 -100 0.1 1 Frequency (MHz) 10 -95 0.1 1 Output Voltage Swing (VPP) 10 Figure 38. Figure 39. TWO-TONE, 3RD-ORDER INTERMODULATION SPURIOUS -40 -50 Load Power at Matched 50W Load 10MHz Spurious Point (dBc) -60 -70 -80 5MHz 1MHz -90 -100 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 Single-Tone Load Power (dBm) Figure 40. Submit Documentation Feedback 13 OPA890 www.ti.com SBOS369 – MAY 2007 TYPICAL CHARACTERISTICS: VS = +5V, Differential At TA = +25°C, Differential Gain = +2V/V, RF = 750Ω, and RL = 400Ω, unless otherwise noted. DIFFERENTIAL SMALL-SIGNAL FREQUENCY RESPONSE 6 3 GD = 2V/V GD = 1V/V R F = 0W DIFFERENTIAL LARGE-SIGNAL FREQUENCY RESPONSE 9 6 3 Normalized Gain (dB) 0 -6 -9 -12 -15 -18 RF = 750W RL = 400W 1 10 Frequency (MHz) GD = 5V/V Gain (dB) -3 4VPP 0 -3 1VPP -6 GD = 10V/V 100 200 -9 1 10 Frequency (MHz) 100 300 Figure 41. DIFFERENTIAL DISTORTION vs LOAD RESISTANCE -70 -75 -80 -85 -90 -95 -100 -105 -110 -115 -120 -125 100 Load Resistance (W) 1k 2nd Harmonic VO = 4VPP f = 1MHz GD = 2V/V 3rd Harmonic -40 -50 Figure 42. DIFFERENTIAL DISTORTION vs FREQUENCY RL = 400W f = 1MHz GD = 2V/V Harmonic Distortion (dBc) Harmonic Distortion (dBc) 3rd Harmonic -60 -70 -80 -90 -100 -110 -120 1 2nd Harmonic 10 Frequency (MHz) Figure 43. DIFFERENTIAL DISTORTION vs OUTPUT VOLTAGE -60 -70 -80 -90 -100 -110 -120 -130 0.1 1 Output Voltage Swing (VPP) 10 2nd Harmonic 3rd Harmonic Figure 44. Harmonic Distortion (dBc) Figure 45. 14 Submit Documentation Feedback OPA890 www.ti.com SBOS369 – MAY 2007 APPLICATION INFORMATION WIDEBAND VOLTAGE-FEEDBACK OPERATION The OPA890 provides an exceptional combination of low quiescent current with a wideband, unity-gain stable, voltage-feedback op amp using a new high slew rate input stage. Typical differential input stages used for voltage-feedback op amps are designed to steer a fixed-bias current to the compensation capacitor, setting a limit to the achievable slew rate. The OPA890 uses an input stage that places the transconductance element between two input buffers, using the combined output currents as the forward signal. As the error voltage increases across the two inputs, an increasing current is delivered to the compensation capacitor. This increasing current provides very high slew rate (500V/µs) while consuming relatively low quiescent current (1.1mA). This exceptional full-power performance comes at the price of a slightly higher input noise voltage than alternative architectures. The 8nV/√Hz input voltage noise for the OPA890 is low for this combination of input stage and low quiescent current. Figure 46 shows the dc-coupled, gain of +2, dual power-supply circuit configuration used as the basis of the ±5V Electrical Characteristics and Typical Characteristics. For test purposes, the input impedance is set to 50Ω with a resistor to ground and the output impedance is set to 50Ω with a series output resistor. Voltage swings reported in the Typical Characteristics are taken directly at the input and output pins, while output powers (dBm) are at the matched 50Ω load. For the circuit of Figure 46, the total effective load will be 100Ω 1.5kΩ. The disable control line is typically left open to ensure normal amplifier operation. Two optional components are included in Figure 46. An additional resistor (324Ω) is included in series with the noninverting input. Combined with the 25Ω dc source resistance looking back towards the signal generator, this configuration gives an input bias current cancelling resistance that matches the 375Ω source resistance seen at the inverting input (see the DC Accuracy and Offset Control section). In addition to the usual power-supply decoupling capacitors to ground, a 0.1µF capacitor is included between the two power-supply pins. In practical printed circuit board (PCB) layouts, this optional-added capacitor typically improves the 2nd-harmonic distortion performance by 3dB to 6dB. 0.1mF +5V 6.8mF + 50W Source 324W DIS VO 50W 50W Load VI 50W OPA890 0.1mF RF 750W RG 750W + -5V 6.8mF 0.1mF Figure 46. DC-Coupled, G = +2, Bipolar Supply, Specification and Test Circuit Figure 47 shows the ac-coupled, gain of +2, single-supply circuit configuration used as the basis of the +5V Electrical Characteristics and Typical Characteristics. Though not a rail-to-rail design, the OPA890 requires minimal input and output voltage headroom compared to other very wideband voltage-feedback op amps. It delivers a 2VPP output swing on a single +5V supply with > 100MHz bandwidth. The key requirement of broadband single-supply operation is to maintain input and output signal swings within the usable voltage ranges at both the input and the output. The circuit of Figure 47 establishes an input midpoint bias using a simple resistive divider from the +5V supply (two 698Ω resistors). The input signal is then ac-coupled into the midpoint voltage bias. The input voltage can swing to within 1.5V of either supply pin, giving a 2VPP input signal range centered between the supply pins. The input impedance matching resistor (59Ω) used for testing is adjusted to give a 50Ω input load when the parallel combination of the biasing divider network is included. Submit Documentation Feedback 15 OPA890 www.ti.com SBOS369 – MAY 2007 +5V +VS MULTIPLYING DAC SINGLE-ENDED OUTPUT TRANSIMPEDANCE AMPLIFIER 0.1mF + 6.8mF 50W Source 0.1mF VI 698W 50W DIS VO 100W VS/2 Multiplyings digital-to-analog converters (DACs), such as the DAC7822, can make good use of the low-power, high slew rate amplifier, OPA890. The frequency response of the schematic shown in Figure 48 is shown in Figure 49. +5V 59W 698W OPA890 RF 750W RG 750W 0.1mF Figure 47. AC-Coupled, G = +2, Single-Supply, Specification and Test Circuit Again, an additional resistor (50Ω, in this case) is included directly in series with the noninverting input. This minimum recommended value provides part of the dc source resistance matching for the noninverting input bias current. It is also used to form a simple parasitic pole to roll off the frequency response at very high frequencies ( > 500MHz) using the input parasitic capacitance to form a bandlimiting pole. The gain resistor (RG) is ac-coupled, giving the circuit a dc gain of +1, which puts the input dc bias voltage (2.5V) at the output as well. The voltage can swing to within 1.35V of either supply pin. Driving a demanding 100Ω load to a midpoint bias is used in this characterization circuit. Higher swings are possible using a lighter load. VDD GND DB0 DB1 VREF DB2 ½ DB3 R1 DAC7822 DB4 RFB DB5 DB6 IOUT1 DB7 IOUT2 DB8 DB9 R2 DB10 R2_3 DB11 R3 -5V 2.5pF +7.5V OPA890 VOUT 0V £ VOUT £ 5V 5.56kW 0.1mF -2.5V Figure 48. DAC Transimpedance Amplifier 83 77 71 Gain (dB) 65 59 53 47 41 100k 1M 10M Frequency (Hz) 100M Figure 49. OPA2890 (as DAC Transimpedance Amplifier) Frequency Response 16 Submit Documentation Feedback OPA890 www.ti.com SBOS369 – MAY 2007 Driving a light load, the OPA890 can output ±4V over ±5V supplies. Setting the reference voltage to –5V results in an output voltage swing from 0V to 5V. In order to optimize the OPA2890 operation for this application, the supply voltages have been adjusted so that the output voltage swing is balanced around mid-supply of the amplifier. Note that as a result of the internal architecture of the multiplying DAC, the IOUT1 output is not high impedance. The IOUT1 output resistance is between 4.5kΩ and 22.1kΩ (excluding code 000h) for a 10kΩ nominal VREF input resistance. IOUT1 output resistance changes are directly related to the code change. This low impedance has multiple effects when a bipolar technology amplifier is used. Some of these effects are: • The noise gain of the amplifier changes for each code. • The output offset voltage of the amplifier changes for each code, because of the input offset voltage. • The input bias current cannot be cancelled. The effects of the input bias current can be reduced, but not eliminated, thereby affecting the total output offset voltage of the amplifier with each code. • The noninverting pin of the amplifier must be tied to ground and cannot be used to create a dc offset on the output amplifier, as is the case for the transimpedance amplifier. The following analysis excludes the input offset current. The total output offset voltage variations because of code changing in the DAC can be expressed as: ∆VOSO = +∆NG {[(RF ROUT1) – RS] + VOS} Notice that most of the error occurs mainly at the first codes (0, 1, 2); excluding these codes from the analysis yields the following results, shown in Table 1. Table 1. DC Accuracy vs Code CODES All codes Excluding code 0 Excluding codes 0 and 1 Excluding codes 0, 1, and 2 TOTAL ERROR DUE TO VOS and IB 3.9LSB 2.5LSB 2LSB 1.83LSB Note that 1LSB = 1.221mV in the example shown in Figure 48 If more precision is required while maintaining the ac performance, a FET-input amplifier (such as the OPA656 or the THS4631) is a good alternative. Figure 48 shows a single-ended output drive implementation. In this circuit, only one side of the complementary output drive signal is used. A dual amplifier, such as the OPA2890, provides both output drivers for the DAC7822. If even lower quiescent current is needed, the OPA2889 can be used instead, with minor modifications. The diagram shows the signal output current connected into the virtual ground summing junction of the OPA890, which is set up as a transimpedance stage or I-V converter. The unused current output of the DAC is connected to ground. The dc gain for this circuit is equal to RF. At high frequencies, the DAC output capacitance produces a zero in the noise gain for the OPA890 that may cause peaking in the closed-loop frequency response. CF is added across RF to compensate for this noise gain peaking. To achieve a flat transimpedance frequency response, the pole in the feedback network should be set to: 1 + 2pR FCF GBP 4pR FC D Where: 4.5kΩ ≤ ROUT1 ≤ 22.1kΩ RF = 10kΩ Using the previous values, the variation of the parallel combination of RF and ROUT1 can be constrained to: 4.19kΩ≤ (RF ROUT1) ≤ 6.88kΩ. In order to optimize the bias current cancellation, we select RS to be the average of those limiting numbers, or RS = (6.88kΩ + 4.19kΩ)/2 = 5.56kΩ. Looking at the variation for each code, the total error (when including all codes) is ~3.9LSB for the OPA890. (2) which gives a closed-loop bandwidth, f–3dB, of approximately: f *3dB + GBP 2pRFC D transimpedance (3) Using the DAC7822 internal output capacitance of 25pF gives a feedback capacitance (CF) of 2.5pF and an 8.8MHz bandwidth. Submit Documentation Feedback 17 OPA890 www.ti.com SBOS369 – MAY 2007 SINGLE-SUPPLY ACTIVE FILTERS The high bandwidth provided by the OPA890, while operating on a single +5V supply, lends itself well to high-frequency active filter designs. Again, the key additional requirement is to establish the dc operating point of the signal near the supply midpoint for highest dynamic range. See Figure 50 for an example design of a 5MHz low-pass Butterworth filter using the Sallen-Key topology. Both the input signal and the gain setting resistor are ac-coupled using 0.1µF blocking capacitors (actually giving band pass response with the low-frequency pole set to 32kHz for the component values shown). As discussed for Figure 47, this configuration allows the midpoint bias formed by the two 1.87kΩ resistors to appear at both the input and output pins. The midband signal gain is set to +4 (12dB) in this case. +5V The capacitor to ground on the noninverting input is intentionally set larger to dominate input parasitic terms. At a gain of +4, the OPA890 on a single supply shows ~30MHz small- and large-signal bandwidth. The resistor values have been slightly adjusted to account for this limited bandwidth in the amplifier stage. Tests of this circuit show a precise 5MHz, –3dB point with a maximally flat passband (above the 32kHz ac-coupling corner), and a maximum stop band attenuation of 24dB at the amplifier –3dB bandwidth of 30MHz. Note that the dc impedance looking out of each input for this circuit has been set to 1.5kΩ to reduce the output offset voltage retaining maximum signal swing for a mid supply nominal operating voltage at the output. 15 1.87kW 100pF 12 9 Gain (dB) 0.1mF 137W VI 432W OPA890 DIS 4VI 5MHz, 2nd-Order, Butterworth Filter 6 3 0 -3 -6 100k 1.87kW 150pF 1.5kW 500W 0.1mF 1M Frequency (Hz) 10M Figure 50. Single-Supply, High-Frequency Active Filter 18 Submit Documentation Feedback OPA890 www.ti.com SBOS369 – MAY 2007 DESIGN-IN TOOLS DEMONSTRATION FIXTURES Two printed circuit boards (PCBs) are available to assist in the initial evaluation of circuit performance using the OPA890 in its two package options. Both of these are offered free of charge as unpopulated PCBs, delivered with a user's guide. The summary information for these fixtures is shown in Table 2. Table 2. Demonstration Board Summary PRODUCT OPA890ID OPA890IDBV PACKAGE SO-8 SOT23-6 ORDERING NUMBER DEM-OPA-SO-1A DEM-OPA-SOT-1A LITERATURE NUMBER SBOU009 SBOU010 MACROMODELS AND APPLICATIONS SUPPORT Computer simulation of circuit performance using SPICE is often useful when analyzing the performance of analog circuits and systems. This practice is particularly true for video and RF amplifier circuits where parasitic capacitance and inductance can have a major effect on circuit performance. A SPICE model for the OPA890 is available through the Texas Instruments web page (www.ti.com). These models do a good job of predicting small-signal ac and transient performance under a wide variety of operating conditions. They do not do as well in predicting the harmonic distortion or dG/dP characteristics. These models do not attempt to distinguish between package types in the small-signal ac performance. The demonstration fixtures can be requested at the Texas Instruments web site (www.ti.com) through the OPA890 product folder. Submit Documentation Feedback 19 OPA890 www.ti.com SBOS369 – MAY 2007 OPERATING SUGGESTIONS OPTIMIZING RESISTOR VALUES Because the OPA890 is a unity-gain stable, voltage-feedback op amp, a wide range of resistor values can be used for the feedback and gain setting resistors. The primary limits on these values are set by dynamic range (noise and distortion) and parasitic capacitance considerations. Usually, for G > 1 applications, the feedback resistor value should be between 200Ω and 1.5kΩ. Below 200Ω, the feedback network presents additional output loading that can degrade the harmonic distortion performance of the OPA890. Above 1.5kΩ, the typical parasitic capacitance (approximately 0.2pF) across the feedback resistor may cause unintentional band-limiting in the amplifier response. The combined impedance of RF RG interacts with the inverting input capacitance, placing an additional pole in the feedback network and thus, a zero in the forward response. Assuming a 2pF total parasitic on the inverting node, having RF RG < 400Ω keeps this pole above 250MHz. By itself, this constraint implies that the feedback resistor RF can increase to several kΩ at high gains. This increase is acceptable, as long as the pole formed by RF and any parasitic capacitance appearing in parallel is kept out of the frequency range of interest. approach the predicted value of (GBP/NG). At a gain of +10V/V, the 13MHz bandwidth shown in the Electrical Characteristics agrees with that predicted using the simple formula and the typical GBP of 130MHz. The OPA890 exhibits minimal bandwidth reduction going to single-supply (+5V) operation as compared with ±5V. This difference in performance occurs because the internal bias control circuitry retains nearly constant quiescent current as the total supply voltage between the supply pins is changed. Inverting Amplifier Operation The OPA890 is a general-purpose, wideband voltage-feedback op amp; therefore, all of the familiar op amp application circuits are available to the designer. Inverting operation is one of the more common requirements and offers several performance benefits. Figure 51 shows a typical inverting configuration where the I/O impedances and signal gain from Figure 46 are retained in an inverting circuit configuration. In the inverting configuration, three key design considerations must be noted. First, the gain resistor (RG) becomes part of the signal channel input impedance. If input impedance matching is desired (which is beneficial whenever the signal is coupled through a cable, twisted-pair, long PCB trace, or other transmission line conductor), RG may be set equal to the required termination value and RF adjusted to give the desired gain. This approach is the simplest, and results in optimum bandwidth and noise performance. However, at low inverting gains, the resultant feedback resistor value can present a significant load to the amplifier output. For an inverting gain of –2V/V, setting RG to 50Ω for input matching eliminates the need for RM but requires a 100Ω feedback resistor. This option has the interesting advantage that the noise gain becomes equal to 2V/V for a 50Ω source impedance—the same as the noninverting circuits considered in the previous section. The amplifier output, however, now sees the 100Ω feedback resistor in parallel with the external load. In general, the feedback resistor should be limited to a range of 200Ω to 1.5kΩ. In this case, it is preferable to increase both the RF and RG values, as shown in Figure 51, and then achieve the input matching impedance with a third resistor (RM) to ground. The total input impedance becomes the parallel combination of RG and RM. BANDWIDTH VERSUS GAIN Noninverting Amplifier Operation Voltage-feedback op amps exhibit decreasing closed-loop bandwidth as the signal gain is increased. In theory, this relationship is described by the gain bandwidth product (GBP) shown in the Electrical Characteristics. Ideally, dividing GBP by the noninverting signal gain (also called the noise gain, or NG) predicts the closed-loop bandwidth. In practice, this relationship only holds true when the phase margin approaches 90°, as it does in high-gain configurations. At low gains (increased feedback factors), most amplifiers exhibit a more complex response with lower phase margin. The OPA890 is compensated to give a slightly peaked response in a noninverting gain of 2V/V (see Figure 46). This compensation results in a typical gain of +2V/V bandwidth of 115MHz, far exceeding that predicted by dividing the 130MHz GBP by 2. Increasing the gain causes the phase margin to approach 90° and the bandwidth to more closely 20 Submit Documentation Feedback OPA890 www.ti.com SBOS369 – MAY 2007 +5V DRIVING CAPACITIVE LOADS + 0.1mF 6.8mF 0.1mF DIS RB 240W 0.1mF OPA890 50W Load RO 50W 50W Source RG 324W RM 59W -5V RF 750W 0.1mF + 6.8mF Figure 51. Gain of –2V/V Example Circuit The second major consideration, touched on in the previous paragraph, is that the signal source impedance becomes part of the noise gain equation and influences the bandwidth. For the example in Figure 51, the RM value combines in parallel with the external 50Ω source impedance, yielding an effective driving impedance of 50Ω 59Ω = 27Ω. This impedance is added in series with RG for calculating the noise gain (NG). The resulting NG is 3.14V/V for Figure 51, as opposed to only 2 if RM could be eliminated as discussed previously. The bandwidth is therefore slightly lower for the gain of –2V/V circuit of Figure 51 than for the gain of +2V/V circuit of Figure 46. The third important consideration in inverting amplifier design is setting the bias current cancellation resistor on the noninverting input (RB). If this resistor is set equal to the total dc resistance looking out of the inverting node, the output dc error (because of the input bias currents) is reduced to (Input Offset Current) × RF. If the 50Ω source impedance is dc-coupled in Figure 51, the total resistance to ground on the inverting input is 351Ω. Combining this resistance in parallel with the feedback resistor gives the value of RB = 240Ω used in this example. To reduce the additional high-frequency noise introduced by this resistor, it is sometimes bypassed with a capacitor. As long as RB < 350Ω, a capacitor is not required because the total noise contribution of all other terms is less than that of the op amp input noise voltage. As a minimum, the OPA890 requires an RB value of 50Ω to damp out parasitic-induced peaking—a direct short to ground on the noninverting input runs the risk of a very high-frequency instability in the input stage. One of the most demanding and yet very common load conditions for an op amp is capacitive loading. Often, the capacitive load is the input of an ADC—including additional external capacitance that may be recommended to improve ADC linearity. A high-speed, high open-loop gain amplifier such as the OPA890 can be very susceptible to decreased stability and closed-loop response peaking when a capacitive load is placed directly on the output pin. When the amplifier open-loop output resistance is considered, this capacitive load introduces an additional pole in the signal path that can decrease the phase margin. Several external solutions to this problem have been suggested. When the primary considerations are frequency response flatness, pulse response fidelity, and/or distortion, the simplest and most effective solution is to isolate the capacitive load from the feedback loop by inserting a series-isolation resistor between the amplifier output and the capacitive load. This solution does not eliminate the pole from the loop response, but rather shifts it and adds a zero at a higher frequency. The additional zero acts to reduce the phase lag from the capacitive load pole, thus increasing the phase margin and improving stability. The Typical Characteristics show the recommended RS versus capacitive load and the resulting frequency response at the load. Parasitic capacitive loads greater than 2pF can begin to degrade the performance of the OPA890. Long PCB traces, unmatched cables, and connections to multiple devices can easily exceed this value. Always consider this effect carefully, and add the recommended series resistor as close as possible to the OPA890 output pin (see the Board Layout Guidelines section). NOISE PERFORMANCE The input-referred voltage noise, and the two input-referred current noise terms, combine to give low output noise under a wide variety of operating conditions. Figure 52 shows the op amp noise analysis model with all the noise terms included. In this model, all noise terms are taken to be noise voltage or current density terms in either nV/√Hz or pA/√Hz. Submit Documentation Feedback 21 OPA890 www.ti.com SBOS369 – MAY 2007 ENI DC ACCURACY AND OFFSET CONTROL OPA890 RF EO RS IBN ERS Ö 4kTRS 4kT RG RG IBI Ö 4kTRF 4kT = 1.6E - 20J at 290°K Figure 52. Op Amp Noise Analysis Model The total output spot noise voltage can be computed as the square root of the sum of all squared output noise voltage contributors. Equation 4 shows the general form for the output noise voltage using the terms shown in Figure 52. EO + E2 ) I BNR S ) 4kTR S NG 2 ) (I BIR F) ) 4kTR FNG NI 2 2 The balanced input stage of a wideband voltage-feedback op amp allows good output dc accuracy in a wide variety of applications. The power-supply current trim for the OPA890 gives even tighter control than comparable amplifiers. Although the high-speed input stage does require relatively high input bias current (+25°C worst case, 1.6µA at each input terminal), the close matching between them may be used to reduce the output dc error caused by this current. The total output offset voltage may be considerably reduced by matching the dc source resistances appearing at the two inputs. This matching reduces the output dc error resulting from the input bias currents to the offset current times the feedback resistor. Evaluating the configuration of Figure 46, and using worst-case +25°C input offset voltage and current specifications, gives a worst-case output offset voltage equal to: ±(NG × VOS(MAX)) ± (RF× IOS(MAX)) = ±(2 × 5mV) ± (750Ω× 0.35µA) = ±11.3mV with NG = noninverting signal gain A fine-scale output offset null or dc operating point adjustment is often required. Numerous techniques are available for introducing dc offset control into an op amp circuit. Most of these techniques eventually reduce to adding a dc current through the feedback resistor. In selecting an offset trim method, one key consideration is the impact on the desired signal path frequency response. If the signal path is intended to be noninverting, the offset control is best applied as an inverting summing signal to avoid interaction with the signal source. If the signal path is intended to be inverting, applying the offset control to the noninverting input may be considered. However, the dc offset voltage on the summing junction will set up a dc current back into the source that must be considered. Applying an offset adjustment to the inverting op amp input can change the noise gain and frequency response flatness. For a dc-coupled inverting amplifier, see Figure 53 for one example of an offset adjustment technique that has minimal impact on the signal frequency response. In this case, the dc offsetting current is brought into the inverting input node through resistor values that are much larger than the signal path resistors. This configuration ensures that the adjustment circuit has minimal effect on the loop gain and thus, the frequency response. (4) Dividing this expression by the noise gain [NG = (1 + RF/RG)] gives the equivalent input-referred spot noise voltage at the noninverting input, as shown in Equation 5. EN + E2 ) I BNR S ) 4kTR S ) NI 2 I BIRF NG 2 ) 4kTRF NG (5) Evaluating these two equations for the OPA890 circuit and component values (see Figure 46) gives a total output spot noise voltage of 17.4nV/√Hz and a total equivalent input spot noise voltage of 8.7nV/√Hz. This total includes the noise added by the bias current cancellation resistor (175Ω) on the noninverting input. This total input-referred spot noise voltage is only slightly higher than the 8nV/√Hz specification for the op amp voltage noise alone. This result will be the case, as long as the impedances appearing at each op amp input are limited to the previously recommend maximum value of 350Ω. Keeping both (RF RG) and the noninverting input source impedance less than 350Ω satisfies both noise and frequency response flatness considerations. Because the resistor-induced noise is relatively negligible, additional capacitive decoupling across the bias current cancellation resistor (RB) for the inverting op amp configuration of Figure 51 is not required. 22 Submit Documentation Feedback OPA890 www.ti.com SBOS369 – MAY 2007 +5V Power-supply decoupling not shown. 0.1mF 226W OPA890 RF 750W VO collector current out of Q1, turning the amplifier off. The supply current in the disable mode is only that required to operate the circuit of Figure 54. Additional circuitry ensures that turn-on time occurs faster than turn-off time (make-before-break). When disabled, the output and input nodes go to a high-impedance state. If the OPA890 is operating at a gain of +1V/V, it shows a very high impedance at the output and exceptional signal isolation. If operating at a gain greater than +1V/V, the total feedback network resistance (RF + RG) appears as the impedance looking back into the output, but the circuit still shows very-high forward and reverse isolation. If configured as an inverting amplifier, the input and output are connected through the feedback network resistance (RF + RG) and the isolation is very poor, as a result. +5V VI RG 324W 5kW -5V 20kW 10kW 0.1mF 5kW ±150mV Output Adjustment VO VI RF RG =- = -2 -5V Figure 53. DC-Coupled, Inverting Gain of -2V/V, with Offset Adjustment THERMAL ANALYSIS DISABLE OPERATION The OPA890 provides an optional disable feature that may be used either to reduce system power or to implement a simple channel multiplexing operation. If the DIS control pin is left unconnected, the OPA890 operates normally. To disable the OPA890, the control pin must be asserted low. Figure 54 shows a simplified internal circuit for the disable control feature. +VS Maximum desired junction temperature sets the maximum allowed internal power dissipation, as described below. In no case should the maximum junction temperature be allowed to exceed +150°C. Operating junction temperature (TJ) is given by TA + PD × θJA. The total internal power dissipation (PD) is the sum of quiescent power (PDQ) and additional power dissipated in the output stage (PDL) to deliver load power. Quiescent power is simply the specified no-load supply current times the total supply voltage across the part. PDL depends on the required output signal and load, but for a grounded resistive load is at a maximum when the output is fixed at a voltage equal to 1/2 of either supply voltage (for equal bipolar supplies). Under this condition, PDL = VS2/(4 × RL) where RL includes feedback network loading. Note that it is the power in the output stage and not into the load that determines internal power dissipation. 80kW Q1 200kW VDIS IS Control -VS 2MW Figure 54. Simplified Disable Control Circuit In normal operation, base current to Q1 is provided through the 2MΩ resistor, while the emitter current through the 80kΩ resistor sets up a voltage drop that is inadequate to turn on the two diodes in the Q1 emitter. As VDIS is pulled low, additional current is pulled through the 80kΩ resistor, eventually turning on those two diodes (≈15µA). At this point, any further current pulled out of VDIS goes through those diodes, holding the emitter-base voltage of Q1 at approximately 0V. This process shuts off the As a worst-case example, compute the maximum TJ using an OPA890IDBV (SOT23-6 package) in the circuit of Figure 46 operating at the maximum specified ambient temperature of +85°C and driving a grounded 100Ω load. PD = 10V × 1.25mA + 52/(4 × (100Ω 79mW 1.5kΩ)) = Maximum TJ = +85°C + (79W × 150°C/W) = +97°C. Although this result is still well below the specified maximum junction temperature, system reliability considerations may require lower operating junction temperatures. The highest possible internal dissipation occurs if the load requires current to be forced into the output for positive output voltages, or sourced from the output for negative output voltages. This configuration puts a high current through a large internal voltage drop in the output transistors. 23 Submit Documentation Feedback OPA890 www.ti.com SBOS369 – MAY 2007 BOARD LAYOUT GUIDELINES Achieving optimum performance with a high-frequency amplifier such as the OPA890 requires careful attention to board layout parasitics and external component types. Recommendations that optimize performance include the following: a. Minimize parasitic capacitance to any ac ground for all of the signal I/O pins. Parasitic capacitance on the output and inverting input pins can cause instability; on the noninverting input, it can react with the source impedance to cause unintentional bandlimiting. To reduce unwanted capacitance, a window around the signal I/O pins should be opened in all of the ground and power planes around those pins. Otherwise, ground and power planes should be unbroken elsewhere on the board. b. Minimize the distance (< 0.25") from the power-supply pins to high-frequency 0.1µF decoupling capacitors. At the device pins, the ground and power-plane layout should not be in close proximity to the signal I/O pins. Avoid narrow power and ground traces to minimize inductance between the pins and the decoupling capacitors. The power-supply connections should always be decoupled with these capacitors. An optional supply decoupling capacitor (0.1µF) across the two power supplies (for bipolar operation) will improve 2nd-harmonic distortion performance. Larger (2.2µF to 6.8µF) decoupling capacitors, effective at lower frequencies, should also be used on the main supply pins. These capacitors may be placed somewhat farther from the device and may be shared among several devices in the same area of the PCB. c. Careful selection and placement of external components preserves the high-frequency performance of the OPA890. Resistors should be a very low reactance type. Surface-mount resistors work best and allow a tighter overall layout. Metal film or carbon composition axially-leaded resistors can also provide good high-frequency performance. Again, keep the leads and PCB traces as short as possible. Never use wirewound type resistors in a high-frequency application. Because the output pin and inverting input pin are the most sensitive to parasitic capacitance, always position the feedback and series output resistor, if any, as close as possible to the output pin. Other network components, such as noninverting input termination resistors, should also be placed close to the package. Where double-side component mounting is 24 allowed, place the feedback resistor directly under the package on the other side of the board between the output and inverting input pins. Even with a low parasitic capacitance shunting the external resistors, excessively high resistor values can create significant time constants that can degrade performance. Good axial metal film or surface-mount resistors have approximately 0.2pF in shunt with the resistor. For resistor values > 1.5kΩ, this parasitic capacitance can add a pole and/or zero below 500MHz that can effect circuit operation. Keep resistor values as low as possible consistent with load driving considerations. The 750Ω feedback used in the Typical Characteristics is a good starting point for design. Note that a direct short is suggested for the unity-gain follower application. d. Connections to other wideband devices on the board may be made with short, direct traces or through onboard transmission lines. For short connections, consider the trace and the input to the next device as a lumped capacitive load. Relatively wide traces (50mils to 100mils) should be used, preferably with ground and power planes opened up around them. Estimate the total capacitive load and set RS from the plot of Recommended RS vs Capacitive Load. Low parasitic capacitive loads (< 5pF) may not need an RS because the OPA890 is nominally compensated to operate with a 2pF parasitic load. Higher parasitic capacitive loads without an RS are allowed as the signal gain increases (increasing the unloaded phase margin). If a long trace is required, and the 6dB signal loss intrinsic to a doubly-terminated transmission line is acceptable, implement a matched impedance transmission line using microstrip or stripline techniques (consult an ECL design handbook for microstrip and stripline layout techniques). A 50Ω environment is normally not necessary on the board, and in fact, a higher impedance environment will improve distortion as shown in the distortion versus load plots. With a characteristic board trace impedance defined (based on board material and trace dimensions), a matching series resistor into the trace from the output of the OPA890 is used as well as a terminating shunt resistor at the input of the destination device. Remember also that the terminating impedance is the parallel combination of the shunt resistor and the input impedance of the destination device; this total effective impedance should be set to match the trace Submit Documentation Feedback OPA890 www.ti.com SBOS369 – MAY 2007 impedance. The high output voltage and current capability of the OPA890 allows multiple destination devices to be handled as separate transmission lines, each with its respective series and shunt terminations. If the 6dB attenuation of a doubly-terminated transmission line is unacceptable, a long trace can be series-terminated at the source end only. Treat the trace as a capacitive load in this case, and set the series resistor value as shown in the plot of Recommended RS vs Capacitive Load. This configuration does not preserve signal integrity as well as a doubly-terminated line. If the input impedance of the destination device is low, there will be some signal attenuation because of the voltage divider formed by the series output into the terminating impedance. e. Socketing a high-speed part such as the OPA890 is not recommended. The additional lead length and pin-to-pin capacitance introduced by the socket can create an extremely troublesome parasitic network that can make it almost impossible to achieve a smooth, stable frequency response. Best results are obtained by soldering the OPA890 directly onto the board. INPUT AND ESD PROTECTION The OPA890 is built using a very high-speed, complementary, bipolar process. The internal junction breakdown voltages are relatively low for these very small geometry devices. These breakdowns are reflected in the Absolute Maximum Ratings table. All device pins are protected with internal ESD protection diodes to the power supplies, as shown in Figure 55. +VCC External Pin Internal Circuitry -VCC Figure 55. Internal ESD Protection These diodes provide moderate protection to input overdrive voltages above the supplies as well. The protection diodes can typically support 30mA continuous current. Where higher currents are possible (for example, in systems with ±15V supply parts driving into the OPA890), current-limiting series resistors should be added into the two inputs. Keep these resistor values as low as possible, because high values degrade both noise performance and frequency response. Submit Documentation Feedback 25 PACKAGE OPTION ADDENDUM www.ti.com 8-Jun-2007 PACKAGING INFORMATION Orderable Device OPA890ID OPA890IDBVR OPA890IDBVT OPA890IDR (1) Status (1) ACTIVE ACTIVE ACTIVE ACTIVE Package Type SOIC SOT-23 SOT-23 SOIC Package Drawing D DBV DBV D Pins Package Eco Plan (2) Qty 8 6 6 8 75 Green (RoHS & no Sb/Br) Lead/Ball Finish CU NIPDAU CU NIPDAU CU NIPDAU CU NIPDAU MSL Peak Temp (3) Level-2-260C-1 YEAR Level-2-260C-1 YEAR Level-2-260C-1 YEAR Level-2-260C-1 YEAR 3000 Green (RoHS & no Sb/Br) 250 Green (RoHS & no Sb/Br) 2500 Green (RoHS & no Sb/Br) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. 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Addendum-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 6-Jun-2007 TAPE AND REEL INFORMATION Pack Materials-Page 1 PACKAGE MATERIALS INFORMATION www.ti.com 6-Jun-2007 Device Package Pins Site Reel Diameter (mm) 180 180 330 Reel Width (mm) 8 8 12 A0 (mm) B0 (mm) K0 (mm) P1 (mm) 8 8 8 W Pin1 (mm) Quadrant 12 12 12 Q3 Q3 Q1 OPA890IDBVR OPA890IDBVT OPA890IDR DBV DBV D 6 6 8 MLA MLA MLA 6.83 6.83 6.9 7.42 7.42 5.4 1.88 1.88 2.0 TAPE AND REEL BOX INFORMATION Device OPA890IDBVR OPA890IDBVT OPA890IDR Package DBV DBV D Pins 6 6 8 Site MLA MLA MLA Length (mm) 0.0 190.0 342.9 Width (mm) 0.0 212.7 336.6 Height (mm) 0.0 31.75 28.58 Pack Materials-Page 2 PACKAGE MATERIALS INFORMATION www.ti.com 6-Jun-2007 Pack Materials-Page 3 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. 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