OPA2357

OPA357 OPA2357 SBOS235C − MARCH 2002− REVISED MAY 2004 250MHz, Rail-to-Rail I/O, CMOS Operational Amplifier with Shutdown FEATURES D D D D D D D D D D D D D UNITY-GAIN BANDWIDTH: 250MHz WIDE BANDWIDTH: 100MHz GBW HIGH SLEW RATE: 150V/ms LOW NOISE: 6.5nV/√Hz RAIL-TO-RAIL I/O HIGH OUTPUT CURRENT: > 100mA EXCELLENT VIDEO PERFORMANCE: Diff Gain: 0.02%, Diff Phase: 0.095 0.1dB Gain Flatness: 40MHz LOW INPUT BIAS CURRENT: 3pA QUIESCENT CURRENT: 4.9mA THERMAL SHUTDOWN SUPPLY RANGE: 2.5V to 5.5V SHUTDOWN IQ < 6mA MicroSIZE AND PowerPAD PACKAGES DESCRIPTION The OPA357 series of high-speed, voltage-feedback CMOS operational amplifiers are designed for video and other applications requiring wide bandwidth. They are unity-gain stable and can drive large output currents. Differential gain is 0.02% and differential phase is 0.09°. Quiescent current is only 4.9mA per channel. The OPA357 series op amps are optimized for operation on single or dual supplies as low as 2.5V (±1.25V) and up to 5.5V (±2.75V). Common-mode input range extends beyond the supplies. The output swing is within 100mV of the rails, supporting wide dynamic range. For applications requiring the full 100mA continuous output current, the single SO-8 PowerPAD version is available. The single version (OPA357), comes in the miniature SOT23-6 and SO-8 PowerPAD packages. The dual version (OPA2357) is offered in the MSOP-10 package. The dual version features completely independent circuitry for lowest crosstalk and freedom from interaction. All are specified over the extended −40°C to +125°C temperature range. APPLICATIONS D D D D D D D D D D VIDEO PROCESSING ULTRASOUND OPTICAL NETWORKING, TUNABLE LASERS PHOTODIODE TRANSIMPEDANCE AMPS ACTIVE FILTERS HIGH-SPEED INTEGRATORS ANALOG-TO-DIGITAL (A/D) CONVERTER INPUT BUFFERS DIGITAL-TO-ANALOG (D/A) CONVERTER OUTPUT AMPLIFIERS BARCODE SCANNERS COMMUNICATIONS OPAx357 RELATED PRODUCTS FEATURES Non-Shutdown Version of OPA357 Family 200MHz GBW, Rail-to-Rail Output, CMOS, Shutdown PRODUCT OPAx354 OPAx355 OPAx356 OPAx350/3 OPAx631 OPAx634 THS412x 200MHz GBW, Rail-to-Rail Output, CMOS 38MHz GBW, Rail-to-Rail Input/Output, CMOS 75MHz BW G = 2, Rail-to-Rail Output 150MHz BW G = 2, Rail-to-Rail Output 100MHz BW, Differential Input/Output, 3.3V Supply V+ − VIN OPA357 +VIN V− Enable VOUT 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 Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright  2002-2004, Texas Instruments Incorporated www.ti.com OPA357 OPA2357 www.ti.com SBOS235C − MARCH 2002− REVISED MAY 2004 ABSOLUTE MAXIMUM RATINGS(1) Supply Voltage, V+ to V− . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5V Signal Input Terminals Voltage(2) . . . (V−) − (0.5V) to (V+) + (0.5V) Current(2) . . . . . . . . . . . . . . . . . . . . . 10mA Enable Input . . . . . . . . . . . . . . . . . . . . (V−) − (0.5V) to (V+) + (0.5V) Output Short-Circuit(3) . . . . . . . . . . . . . . . . . . . . . . . . . . Continuous Operating Temperature . . . . . . . . . . . . . . . . . . . . . . −55°C to +150°C Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . . −65°C to +150°C Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +150°C Lead Temperature (soldering, 10s) . . . . . . . . . . . . . . . . . . . . . +300°C (1) 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 supported. (2) Input terminals are diode-clamped to the power-supply rails. Input signals that can swing more than 0.5V beyond the supply rails should be current limited to 10mA or less. (3) Short-circuit to ground, one amplifier per package. ELECTROSTATIC DISCHARGE SENSITIVITY 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. PACKAGE/ORDERING INFORMATION(1) PRODUCT OPA357 PACKAGE−LEAD SO-8 PowerPAD PACKAGE DESIGNATOR(1) DDA SPECIFIED TEMPERATURE RANGE −40°C to +125°C PACKAGE MARKING OPA357A ORDERING NUMBER OPA357AIDDA OPA357AIDDAR OPA357AIDBVT OPA357AIDBVR OPA2357AIDGST OPA2357AIDGSR TRANSPORT MEDIA, QUANTITY Rails, 97 Tape and Reel, 2500 Tape and Reel, 250 Tape and Reel, 3000 Tape and Reel, 250 Tape and Reel, 2500 ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ ″ OPA357 OPA2357 SOT23-6 MSOP-10 DBV DGS −40°C to +125°C −40°C to +125°C OADI BBG (1) For the most current package and ordering information, see the Package Option Addendum located at the end of this data sheet. PIN CONFIGURATION Top View OPA357 Out V− +In OPA357 6 V+ Enable − In NC (2 ) − In +In V− OPA2357 8 7 6 5 Enable V+ Out NC (2 ) Out A − In A +In A V− Enable A 1 OADI 2 3 SOT23(1) 1 2 3 4 SO PowerPAD(3) 1 2 A 3 B 4 5 MSOP−10 10 V+ 9 8 7 6 Out B − In B +In B Enable B 5 4 NOTES: (1) Pin 1 of the SOT23-6 is determined by orienting the package marking as indicated in the diagram. (2) NC means no internal connection. (3) PowerPAD should be connected to V− or left floating. 2 OPA357 OPA2357 www.ti.com SBOS235C − MARCH 2002− REVISED MAY 2004 ELECTRICAL CHARACTERISTICS: VS = +2.7V to +5.5V Single-Supply Boldface limits apply over the temperature range, TA = −40°C to +125°C. All specifications at TA = +25°C, RF = 0Ω , RL = 1kΩ connected to VS/2, unless otherwise noted. OPA357AI OPA2357AI PARAMETER OFFSET VOLTAGE Input Offset Voltage vs Temperature vs Power Supply VOS VS = +5V Specified Temperature Range Specified Temperature Range VS = +2.7V to +5.5V, VCM = (VS/2) − 0.15V Specified Temperature Range ±2 +4 ±200 ±800 ±900 3 ±1 f = 1MHz f = 1MHz 6.5 50 ±50 ±50 ±8 +10 mV mV µV/°C µV/V µV/V pA pA nV/√Hz fA/√Hz (V+) + (0.1V) 80 68 V dB dB dB dB 1013 || 2 1013 || 2 AOL VS = +5V, +0.3V < VO < +4.7V VS = +5V, +0.4V < VO < +4.6V G = +1, VO = 100mVPP, RF = 25Ω G = +2, VO = 100mVPP G = +10 G = +2, VO = 100mVPP VS = +5V, G = +1, 4V Step VS = +5V, G = +1, 2V Step VS = +3V, G = +1, 2V Step G = +1, VO = 200mVPP, 10% to 90% G = 1, VO = 2VPP, 10% to 90% Settling Time, 0.1% 0.01% Overload Recovery Time Harmonic Distortion 2nd-Harmonic 3rd-Harmonic Differential Gain Error Differential Phase Error Channel-to-Channel Crosstalk, OPA2357 CONDITIONS MIN TYP MAX UNITS dVOS/dT PSRR INPUT BIAS CURRENT Input Bias Current Input Offset Current NOISE Input Voltage Noise Density Current Noise Density INPUT VOLTAGE RANGE Common-Mode Voltage Range Common-Mode Rejection Ratio VCM CMRR (V−) − (0.1) VS = +5.5V, −0.1V < VCM < +3.5V Specified Temperature Range VS = +5.5V, −0.1V < VCM < +5.6V Specified Temperature Range INPUT IMPEDANCE Differential Common-Mode OPEN-LOOP GAIN Specified Temperature Range FREQUENCY RESPONSE Small-Signal Bandwidth Gain-Bandwidth Product Bandwidth for 0.1dB Gain Flatness Slew Rate f−3dB f−3dB GBW f0.1dB SR 250 90 100 40 150 130 110 2 11 30 60 VIN S Gain = VS G = +1, f = 1MHz, VO = 2VPP, RL = 200Ω, VCM = 1.5V G = +1, f = 1MHz, VO = 2VPP, RL = 200Ω, VCM = 1.5V NTSC, RL = 150Ω NTSC, RL = 150Ω f = 5MHz VS = +5V, RL = 1kΩ, AOL > 94dB VS = +5V, RL = 1kΩ, AOL > 90dB VS = +5V VS = +3V f < 100kHz RO 5 −75 −83 0.02 0.09 −100 MHz MHz MHz MHz V/µs V/µs V/µs ns ns ns ns ns dBc dBc % degrees dB 94 90 Ω || pF Ω || pF dB dB 66 64 56 55 en in IB IOS 110 Rise-and-Fall Time VS = +5V, G = +1, 2V Output Step OUTPUT Voltage Output Swing from Rail Specified Temperature Range Output Current(1)(2), Single, Dual Closed-Loop Output Impedance Open-Loop Output Resistance IO 0.1 100 50 0.05 35 0.3 0.4 V V mA mV Ω Ω (1) See typical characteristics Output Voltage Swing vs Output Current. (2) Specified by design. 3 OPA357 OPA2357 www.ti.com SBOS235C − MARCH 2002− REVISED MAY 2004 ELECTRICAL CHARACTERISTICS: VS = +2.7V to +5.5V Single-Supply (continued) Boldface limits apply over the temperature range, TA = −40°C to +125°C. All specifications at TA = +25°C, RF = 0Ω , RL = 1kΩ connected to VS/2, unless otherwise noted. OPA357AI OPA2357AI PARAMETER POWER SUPPLY Specified Voltage Range Operating Voltage Range Quiescent Current (per amplifier) IQ VS = +5V, Enabled, IO = 0 Specified Temperature Range VS 2.7 2.5 to 5.5 4.9 6 7.5 5.5 V V mA mA CONDITIONS MIN TYP MAX UNITS ENABLE/SHUTDOWN FUNCTION Disabled (logic−LOW Threshold) Enabled (logic−HIGH Threshold) Logic Input Current Turn-On Time Turn-Off Time Off Isolation Quiescent Current (per amplifier) THERMAL SHUTDOWN Junction Temperature Shutdown Reset from Shutdown TEMPERATURE RANGE Specified Range Operating Range Storage Range Thermal Resistance SOT23-6 SO-8 PowerPAD MSOP-10 (1) See typical characteristics Output Voltage Swing vs Output Current. (2) Specified by design. −40 −55 −65 +125 +150 +150 150 65 150 °C °C °C °C/W °C/W °C/W °C/W TJ +160 +140 °C °C G = +1, 5MHz, RL = 10Ω Logic LOW 2 200 100 30 74 3.4 6 0.8 V V nA ns ns dB µA qJA 4 OPA357 OPA2357 www.ti.com SBOS235C − MARCH 2002− REVISED MAY 2004 TYPICAL CHARACTERISTICS At TA = +25°C, VS = 5V, G = +1, RF = 0Ω, RL = 1kΩ, and connected to VS/2, unless otherwise noted. NONINVERTING SMALL−SIGNAL FREQUENCY RESPONSE 3 VO = 0.1VPP 0 Normalized Gain (dB) −3 −6 −9 − 12 − 15 100k G = +2, RF = 604Ω G = +5, RF = 604 Ω G = +10, RF = 604Ω G = +1 RF = 25Ω Normalized Gain (dB) 3 INVERTING SMALL− SIGNAL FREQUENCY RESPONSE VO = 0.1VPP, RF = 604Ω 0 −3 G = −1 −6 G = −5 −9 G = − 10 − 12 − 15 100k G = −2 1M 10M Frequency (Hz) 100M 1G 1M 10M Frequency (Hz) 100M 1G NONINVERTING SMALL−SIGNAL STEP RESPONSE NONINVERTING LARGE−SIGNAL STEP RESPONSE Time (20ns/div) Output Voltage (500mV/div) Output Voltage (40mV/div) Time (20ns/div) 0.1dB GAIN FLATNESS LARGE−SIGNAL DISABLE/ENABLE RESPONSE 0.5 0.4 VO = 0.1VPP Output Voltage (400mV/div) Normalized Gain (dB) 0.3 0.2 0.1 0 − 0.1 − 0.2 − 0.3 − 0.4 − 0.5 100k 1M G = +2 RF = 604 Ω G = +1 RF = 25 Ω Enabled 4.5 3.5 2.5 1.5 Disabled VOUT fIN = 5MHz Time (200ns/div) 0.5 Disable Voltage (V) 10M Frequency (Hz) 100M 1G 5 OPA357 OPA2357 www.ti.com SBOS235C − MARCH 2002− REVISED MAY 2004 TYPICAL CHARACTERISTICS (continued) At TA = +25°C, VS = 5V, G = +1, RF = 0Ω, RL = 1kΩ, and connected to VS/2, unless otherwise noted. HARMONIC DISTORTION vs OUTPUT VOLTAGE − 50 − 60 − 70 2nd−Harmonic − 80 − 90 − 100 0 1 3rd−Harmonic 2 Output Voltage (VPP) 3 4 G = −1 f = 1MHz RL = 200Ω − 50 − 60 − 70 HARMONIC DISTORTION vs NONINVERTING GAIN VO = 2VPP f = 1MHz RL = 200Ω Harmonic Distortion (dBc) Harmonic Distortion (dBc) 2nd−Harmonic − 80 − 90 3rd−Harmonic − 100 1 Gain (V/V) 10 HARMONIC DISTORTION vs INVERTING GAIN − 50 − 60 − 70 2nd−Harmonic − 80 − 90 3rd−Harmonic − 100 1 Gain (V/V) 10 − 100 100k VO = 2VPP f = 1MHz R L = 200Ω − 50 − 60 − 70 HARMONIC DISTORTION vs FREQUENCY G = +1 VO = 2VPP RL = 200Ω VCM = 1.5V 2nd−Harmonic − 80 − 90 3rd−Harmonic Harmonic Distortion (dBc) Harmonic Distortion (dBc) 1M Frequency (Hz) INPUT VOLTAGE AND CURRENT NOISE SPECTRAL DENSITY vs FREQUENCY 10M HARMONIC DISTORTION vs LOAD RESISTANCE − 50 − 60 − 70 − 80 − 90 − 100 100 RL (Ω) 1k 3rd−Harmonic G = +1 VO = 2VPP f = 1MHz VCM = 1.5V 2nd−Harmonic 10k Harmonic Distortion (dBc) Voltage Noise (nV/√ Hz), Current Noise (fA/√ Hz) 1k Voltage Noise 100 Current Noise 10 1 10 100 1k 10k 100k 1M 10M 100M Frequency (Hz) 6 OPA357 OPA2357 www.ti.com SBOS235C − MARCH 2002− REVISED MAY 2004 TYPICAL CHARACTERISTICS (continued) At TA = +25°C, VS = 5V, G = +1, RF = 0Ω, RL = 1kΩ, and connected to VS/2, unless otherwise noted. FREQUENCY RESPONSE FOR VARIOUS RL 3 RL = 10kΩ 0 Normalized Gain (dB) Normalized Gain (dB) −3 −6 −9 RL = 50Ω − 12 − 15 100k G = +1 RF = 0Ω VO = 0.1VPP CL = 0pF 9 6 3 0 −3 −6 −9 − 12 1M 10M Frequency (Hz) 100M 1G − 15 100k FREQUENCY RESPONSE FOR VARIOUS CL G = +1 VO = 0.1VPP RS = 0Ω CL = 100pF RL = 1k Ω RL = 100Ω CL = 47pF CL = 5.6pF 1M 10M Frequency (Hz) 100M 1G RECOMMENDED RS vs CAPACITIVE LOAD 160 140 120 100 RS (Ω) 80 60 VIN RS OPA357 CL FREQUENCY RESPONSE vs CAPACITIVE LOAD 3 G = +1, VO = 0.1VPP CL = 47pF, RS = 140 Ω CL = 100pF, RS = 120 Ω CL = 5.6pF, RS = 0Ω For 0.1dB Flatness Normalized Gain (dB) 0 −3 −6 −9 VIN OPA357 RS VO CL 1kΩ 40 20 0 1 VO 1kΩ − 12 − 15 100k 10 100 Capacitive Load (pF) 1k 1M 10M Frequency (Hz) 100M 1G COMMON−MODE REJECTION RATIO AND POWER−SUPPLY REJECTION RATIO vs FREQUENCY 100 Open−Loop Phase (degrees) Open−Loop Gain (dB) CMRR 80 CMRR, PSRR (dB) PSRR+ 60 PSRR− 40 180 160 140 120 100 80 60 40 20 0 − 20 0 10k 100k 1M 10M Frequency (Hz) 100M 1G − 40 10 100 OPEN−LOOP GAIN AND PHASE Phase Gain 20 1k 10k 100k 1M Frequency (Hz) 10M 100M 1G 7 OPA357 OPA2357 www.ti.com SBOS235C − MARCH 2002− REVISED MAY 2004 TYPICAL CHARACTERISTICS (continued) At TA = +25°C, VS = 5V, G = +1, RF = 0Ω, RL = 1kΩ, and connected to VS/2, unless otherwise noted. COMPOSITE VIDEO DIFFERENTIAL GAIN AND PHASE 0.8 0.7 Input Bias Current (pA) dG/dP (%/degrees) 0.6 0.5 0.4 0.3 0.2 0.1 0 1 2 3 4 Number of 150Ω Loads OUTPUT VOLTAGE SWING vs OUTPUT CURRENT FOR VS = 3V 3 7 6 Supply Current (mA) dG 1 − 55 dP 1k 10k INPUT BIAS CURRENT vs TEMPERATURE 100 10 − 35 − 15 5 25 45 65 Temperature (_ C) 85 105 125 135 SUPPLY CURRENT vs TEMPERATURE VS = 5V 5 4 VS = 2.5V 3 2 1 Output Voltage (V) 2 +125_ C 1 +25_ C − 55_ C 0 0 20 40 60 80 100 120 Output Current (mA) 0 − 55 − 35 − 15 5 25 45 65 Temperature (_ C) 85 105 125 135 OUTPUT VOLTAGE SWING vs OUTPUT CURRENT FOR VS = 5V 5 4.5 4 Shutdown Current (µA) 4 Output Voltage (V) 3.5 3 2.5 2 1.5 1 0.5 0 0 25 50 75 100 125 150 175 200 Output Current (mA) 0 − 55 SHUTDOWN CURRENT vs TEMPERATURE VS = 5.5V 3 +125_ C 2 +25_ C − 55_ C VS = 5V 1 VS = 3V VS = 2.5V − 35 − 15 5 25 45 65 Temperature (_ C) 85 105 125 135 8 OPA357 OPA2357 www.ti.com SBOS235C − MARCH 2002− REVISED MAY 2004 TYPICAL CHARACTERISTICS (continued) At TA = +25°C, VS = 5V, G = +1, RF = 0Ω, RL = 1kΩ, and connected to VS/2, unless otherwise noted. DISABLE FEEDTHROUGH vs FREQUENCY 0 − 20 Feedthrough (dB) − 40 − 60 Forward − 80 − 100 − 120 100k Reverse VDISABLE = 0 RL = 10Ω Output Impedance (Ω) 100 CLOSED−LOOP OUTPUT IMPEDANCE vs FREQUENCY 10 1 0.1 OPA357 ZO 1M 10M Frequency (Hz) 100M 1G 0.01 100k 1M 10M Frequency (Hz) 100M 1G MAXIMUM OUTPUT VOLTAGE vs FREQUENCY 6 VS = 5.5V 5 Output Voltage (VPP) 4 3 VS = 2.7V 2 1 0 1 10 Frequency (MHz) OPEN−LOOP GAIN vs TEMPERATURE 120 RL = 1kΩ Open−Loop Gain (dB) 110 100 Output Error (%) Maximum Output Voltage without Slew−Rate Induced Distortion 0.5 0.4 0.3 0.2 0.1 0 − 0.1 − 0.2 − 0.3 − 0.4 − 0.5 0 10 OUTPUT SETTLING TIME TO 0.1% VO = 2VPP 20 30 40 50 60 70 80 90 100 Time (ns) OFFSET VOLTAGE PRODUCTION DISTRIBUTION 100 90 80 70 − 55 − 35 − 15 5 25 45 65 Temperature (_ C) 85 105 125 135 − 8 −7 −6 − 5 −4 − 3 − 2 −1 0 1 2 3 Offset Voltage (mV) 456 78 Population 9 OPA357 OPA2357 www.ti.com SBOS235C − MARCH 2002− REVISED MAY 2004 TYPICAL CHARACTERISTICS (continued) At TA = +25°C, VS = 5V, G = +1, RF = 0Ω, RL = 1kΩ, and connected to VS/2, unless otherwise noted. COMMON−MODE REJECTION RATIO AND POWER−SUPPLY REJECTION RATIO vs TEMPERATURE 100 Crosstalk, Input− Referred (dB) CHANNEL−TO−CHANNEL CROSSTALK 0 − 20 − 40 − 60 − 80 − 100 − 120 100k OPA2357 90 CMRR, PSRR (dB) Common−Mode Rejection Ratio 80 Power−Supply Rejection Ratio 70 60 50 − 55 − 35 − 15 5 25 45 65 85 105 125 135 Temperature (_ C) 1M 10M Frequency (Hz) 100M 1G 10 OPA357 OPA2357 www.ti.com SBOS235C − MARCH 2002− REVISED MAY 2004 APPLICATIONS INFORMATION The OPA357 is a CMOS, rail-to-rail I/O, high-speed, voltage-feedback operational amplifier designed for video, high-speed, and other applications. It is available as a single or dual op amp. The amplifier features a 100MHz gain bandwidth, and 150V/µs slew rate, but it is unity-gain stable and can be operated as a +1V/V voltage follower. The Enable input can be modeled as a CMOS input gate with a 100kΩ pull-up resistor to V+. This pin should be connected to a valid high or low voltage or driven, not left open circuit. The enable time is 100ns and the disable time is only 30ns. This allows the OPA357 to be operated as a gated amplifier, or to have its output multiplexed onto a common output bus. When disabled, the output assumes a high-impedance state. OPERATING VOLTAGE The OPA357 is specified over a power-supply range of +2.7V to +5.5V (±1.35V to ±2.75V). However, the supply voltage may range from +2.5V to +5.5V (±1.25V to ±2.75V). Supply voltages higher than 7.5V (absolute maximum) can permanently damage the amplifier. Parameters that vary over supply voltage or temperature are shown in the Typical Characteristics section of this data sheet. RAIL-TO-RAIL INPUT The specified input common-mode voltage range of the OPA357 extends 100mV beyond the supply rails. This is achieved with a complementary input stagean N-channel input differential pair in parallel with a P-channel differential pair, as shown in Figure 1. The N-channel pair is active for input voltages close to the positive rail, typically (V+) − 1.2V to 100mV above the positive supply, while the P-channel pair is on for inputs from 100mV below the negative supply to approximately (V+) − 1.2V. There is a small transition region, typically (V+) − 1.5V to (V+) − 0.9V, in which both pairs are on. This 600mV transition region can vary ±500mV with process variation. Thus, the transition region (both input stages on) can range from (V+) − 2.0V to (V+) − 1.5V on the low end, up to (V+) − 0.9V to (V+) − 0.4V on the high end. A double-folded cascode adds the signal from the two input pairs and presents a differential signal to the class AB output stage. ENABLE FUNCTION The OPA357’s Enable function is implemented using a Schmitt trigger. The amplifier is enabled by applying a TTL HIGH voltage level (referenced to V−) to the Enable pin. Conversely, a TTL LOW voltage level (referenced to V−) will disable the amplifier, reducing its supply current from 4.9mA to only 3.4µA per amplifier. Independent Enable pins are available for each channel (dual version), providing maximum design flexibility. For portable battery-operated applications, this feature can be used to greatly reduce the average current and thereby extend battery life. V+ Reference Current VIN+ VIN− VBIAS1 Class AB Control Circuitry VO VBIAS2 V− (Ground) Figure 1. Simplified Schematic 11 OPA357 OPA2357 www.ti.com SBOS235C − MARCH 2002− REVISED MAY 2004 RAIL-TO-RAIL OUTPUT A class AB output stage with common-source transistors is used to achieve rail-to-rail output. For high-impedance loads (> 200Ω), the output voltage swing is typically 100mV from the supply rails. With 10Ω loads, a useful output swing can be achieved while maintaining high open-loop gain. See the typical characteristic curve Output Voltage Swing vs Output Current. R2 10kΩ C1 200pF +5V R1 100kΩ 1µ F OUTPUT DRIVE The OPA357’s output stage can supply a continuous output current of ±100mA and still provide approximately 2.7V of output swing on a 5V supply, as shown in Figure 2. For maximum reliability, it is not recommended to run a continuous DC current in excess of ±100mA. Refer to the typical characteristic curve Output Voltage Swing vs Output Current. For supplying continuous output currents greater than ±100mA, the OPA357 may be operated in parallel as shown in Figure 3. The OPA357 will provide peak currents up to 200mA, which corresponds to the typical short-circuit current. Therefore, an on-chip thermal shutdown circuit is provided to protect the OPA357 from dangerously high junction temperatures. At 160°C, the protection circuit will shut down the amplifier. Normal operation will resume when the junction temperature cools to below 140°C. R3 100kΩ + − R5 = 1Ω OPA2357 2V In = 200mA Out, as Shown R6 = 1Ω OPA2357 RSHUNT 1Ω R4 10kΩ Laser Diode Figure 3. Parallel Operation VIDEO The OPA357 output stage is capable of driving standard back-terminated 75Ω video cables, as shown in Figure 4. By back-terminating a transmission line, it does not exhibit a capacitive load to its driver. A properly back-terminated 75Ω cable does not appear as capacitance; it presents only a 150Ω resistive load to the OPA357 output. R2 1kΩ C1 50pF R1 10kΩ 1µF V+ + − V1 5V +5V OPA357 R3 10kΩ V− RSHUNT R4 1kΩ Laser Diode 604Ω +2.5V Video In 75Ω +2.5V OPA357 75Ω Video Output + − VIN 1V In = 100mA Out, as Shown To enable, connect to V+ or drive with logic. 604Ω Figure 2. Laser Diode Driver Figure 4. Single-Supply Video Line Driver 12 OPA357 OPA2357 www.ti.com SBOS235C − MARCH 2002− REVISED MAY 2004 The OPA357 can be used as an amplifier for RGB graphic signals, which have a voltage of zero at the video black level, by offsetting and AC-coupling the signal. See Figure 5. 604Ω +3V + 1µ F 10nF V+ R1 604Ω 1/2 OPA2357 75Ω Red 75Ω Red(1) R2 V+ R1 604Ω 1/2 OPA2357 Green(1) 75Ω Green 75Ω R2 604Ω NOTE: (1) Source video signal offset 300mV above ground to accomodate op amp swing−to−ground capability. 604Ω +3V + V+ R1 604Ω 1 µF 10nF 75Ω Blue(1) OPA357 Blue 75Ω R2 Figure 5. RGB Cable Driver 13 OPA357 OPA2357 www.ti.com SBOS235C − MARCH 2002− REVISED MAY 2004 WIDEBAND VIDEO MULTIPLEXING One common application for video speed amplifiers which include an enable pin is to wire multiple amplifier outputs together, then select which one of several possible video inputs to source onto a single line. This simple Wired-OR Video Multiplexer can be easily implemented using the OPA357; see Figure 6. +2.5V + 1µF 10nF Signal #1 49.9Ω A O PA357 + 1µF 10nF − 2.5V 1kΩ 49.9Ω VOUT 49.9Ω 1kΩ +2.5V + 1µF 10nF Signal #2 49.9Ω B O PA357 + 1µF 10nF − 2.5V 1kΩ 1kΩ HCO4 BON Select AON Figure 6. Multiplexed Output 14 OPA357 OPA2357 www.ti.com SBOS235C − MARCH 2002− REVISED MAY 2004 DRIVING ANALOG−TO−DIGITAL CONVERTERS The OPA357 series op amps offer 60ns of settling time to 0.01%, making them a good choice for driving high- and medium-speed sampling A/D converters and reference circuits. The OPA357 series provide an effective means of buffering the A/D converter’s input capacitance and resulting charge injection while providing signal gain. See Figure 7 for the OPA357 driving an A/D converter. With the OPA357 in an inverting configuration, a capacitor across the feedback resistor can be used to filter high-frequency noise in the signal; see Figure 7. resistance, to create a pole in the small-signal response that degrades the phase margin. Refer to the typical characteristic curve Frequency Response for Various CL for details. The OPA357’s topology enhances its ability to drive capacitive loads. In unity gain, these op amps perform well with large capacitive loads. Refer to the typical characteristic curves Recommended RS vs Capacitive Load and Frequency Response vs Capacitive Load for details. One method of improving capacitive load drive in the unity-gain configuration is to insert a 10Ω to 20Ω resistor in series with the output, as shown in Figure 8. This significantly reduces ringing with large capacitive loadssee the typical characteristic curve Frequency Response vs Capacitive Load. However, if there is a resistive load in parallel with the capacitive load, RS creates a voltage divider. This introduces a DC error at the output and slightly reduces output swing. This error may be insignificant. For instance, with RL = 10kΩ and RS = 20Ω, there is only about a 0.2% error at the output. CAPACITIVE LOAD AND STABILITY The OPA357 series op amps can drive a wide range of capacitive loads. However, all op amps under certain conditions may become unstable. Op amp configuration, gain, and load value are just a few of the factors to consider when determining stability. An op amp in unity-gain configuration is most susceptible to the effects of capacitive loading. The capacitive load reacts with the op amp’s output resistance, along with any additional load +5V 330pF 5kΩ VIN 5kΩ V+ 5kΩ OPA357 +In 0.1µF − In ADS7818, ADS7861, or ADS7864 12− A/D Converter Bit GND VREF +2.5V VIN = 0V to − 5V for 0V to 5V output. NOTE: A/D Converter Input = 0V to VREF Figure 7. The OPA357 in Inverting Configuration Driving an A/D Converter V+ RS OPA357 VIN RL To enable, connect to V+ or drive with logic. CL VOUT Figure 8. Series Resistor in Unity-Gain Configuration Improves Capacitive Load Drive 15 OPA357 OPA2357 www.ti.com SBOS235C − MARCH 2002− REVISED MAY 2004 WIDEBAND TRANSIMPEDANCE AMPLIFIER Wide bandwidth, low input bias current, and low input voltage and current noise make the OPA357 an ideal wideband photodiode transimpedance amplifier for low-voltage single-supply applications. Low-voltage noise is important because photodiode capacitance causes the effective noise gain of the circuit to increase at high frequency. The key elements to a transimpedance design, as shown in Figure 9, are the expected diode capacitance (including the parasitic input common-mode and differential-mode input capacitance (2 + 2)pF for the OPA357), the desired transimpedance gain (RF), and the Gain Bandwidth Product (GBP) for the OPA357 (100MHz). With these 3 variables set, the feedback capacitor value (CF) may be set to control the frequency response. PCB LAYOUT Good high-frequency printed circuit board (PCB) layout techniques should be employed for the OPA357. Generous use of ground planes, short and direct signal traces, and a suitable bypass capacitor located at the V+ pin will assure clean, stable operation. Large areas of copper also provides a means of dissipating heat that is generated in normal operation. Sockets are definitely not recommended for use with any high-speed amplifier. A 10nF ceramic bypass capacitor is the minimum recommended value; adding a 1µF or larger tantalum capacitor in parallel can be beneficial when driving a low-resistance load. Providing adequate bypass capacitance is essential to achieving very low harmonic and intermodulation distortion. CF