OPA2662

OP A26 62 OPA2662 OP A26 62 Dual, Wide Bandwidth OPERATIONAL TRANSCONDUCTANCE AMPLIFIER FEATURES q 370MHz BANDWIDTH q 58mA/ns SLEW RATE q HIGH OUTPUT CURRENT: ±75mA q 400Mbit/s DATA RATE q VOLTAGE-CONTROLLED CURRENT SOURCE q ENABLE/DISABLE FUNCTION DESCRIPTION The OPA2662 is a versatile driver device for ultra wide-bandwidth systems, including high-resolution video, RF and IF circuitry, communications and test equipment. The OPA2662 includes two power voltage-controlled current sources, or operational transconductance amplifiers (OTAs), in a 16-pin DIP or SOL-16 package and is specified for the extended industrial temperature range (–40°C to +85°C). The output current is zero-for-zero differential input voltage. The OTAs provide a 250MHz large-signal bandwidth, a 58mA/ns slew rate, and each current source delivers up to ±75mA output current. The transconductance of both OTAs can be adjusted between pin 5 and –VCC by an external resistor, allowing bandwidth, quiescent current, harmonic distortion and gain trade-offs to be optimized. The output current can be set with a degeneration resistor between the emitter and GND. The current mirror ratio between the collector and emitter currents is fixed to three. Switching stages compatible to logic TTL levels make it possible to turn each OTA separately on within 30ns and off within 200ns at full power. I (mA) 80 70 IC 60 50 40 30 20 IE APPLICATIONS q HEAD DRIVE AMPLIFIER FOR ANALOG/ DIGITAL VIDEO TAPES AND DATA RECORDERS q LED AND LASER DIODE DRIVER q HIGH CURRENT VIDEO BUFFER OR LINE DRIVER q RF OUTPUT STAGE DRIVER q HIGH DENSITY DISK DRIVES +VCCOUT (16) B +1 (2,7) EN (3, 6) E (10,15) C (11,14) –1 –0.8 –0.6 –0.4 0.2 –10 –20 –30 –40 –50 0.4 0.6 0.8 1 VIN (V) (9) –VCCOUT 1/2 OPA2662 –60 –70 –80 OTA Transfer Characteristics International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111 • Twx: 910-952-1111 Internet: http://www.burr-brown.com/ • FAXLine: (800) 548-6133 (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132 © 1991 Burr-Brown Corporation PDS-1129D Printed in U.S.A. August, 1994 SPECIFICATIONS ELECTRICAL DC-SPECIFICATIONS At VCC = ±5V, RQ = 750Ω, TA = +25°C, and configured as noted under “CONDITIONS”. OPA2662AP, AU PARAMETER OTA INPUT OFFSET VOLTAGE Initial vs Temperature vs Supply (tracking) vs Supply (non-tracking) vs Supply (non-tracking) Matching OTA B-INPUT BIAS CURRENT Initial vs Temperature vs Supply (tracking) vs Supply (non-tracking) vs Supply (non-tracking) Matching OTA C-OUTPUT BIAS CURRENT Initial vs Temperature vs Supply (tracking) vs Supply (non-tracking) vs Supply (non-tracking) Matching B-INPUT IMPEDANCE Impedance OTA INPUT NOISE Input Noise Voltage Density Output Noise Current Density Signal-to-Noise Ratio OTA C-RATED OUTPUT Output Voltage Compliance Output Current Output Impedance, rC OTA E-RATED OUTPUT Voltage Output DC Current Output Voltage Gain CONDITIONS RE = 50kΩ, RC = 40Ω VCC = ±4.5V to ±5.5V, RE = 50kΩ, RC = 1kΩ VCC = +4.5V to +5.5V, RE = 50kΩ, RC = 1kΩ VCC = –4.5V to –5.5V, RE = 50kΩ, RC = 1kΩ MIN TYP 12 35 27 15 40 2 1 –5 60 160 40 0.2 0.5 1.5 72 236 92 0.06 4.5 || 1.5 4.4 0.09 97 ±3.4 ±75 4.5 || 6.5 ±3.0 ±25 0.86 0.98 16 || 2.2 ±4.5 ±3 +15 ±5.5 ±6 +18 MAX ±30 UNITS mV µV/°C dB dB dB mV µA nA/°C nA/V nA/V nA/V µA mA µA/°C µA/V µA/V µA/V mA MΩ || pF nV/√Hz nA/√Hz dB V mA kΩ || pF V mA V/V V/V Ω || pF VDC VDC mA mA ±7 –1/+5 RE = 100Ω, RC = 40Ω VCC = ±4.5V to ±5.5V, RE = 50kΩ, RC = 1kΩ VCC = +4.5V to +5.5V, RE = 50kΩ, RC = 1kΩ VCC = –4.5V to –5.5V, RE = 50kΩ, RC = 1kΩ RE = 100Ω, RC = 1kΩ ±1 –0.5/+1.5 VCC = ±4.5V to ±5.5V VCC = +4.5V to +5.5V VCC = –4.5V to –5.5V ±0.5 IQ = ±17mA f = 20kHz to 100MHz S/N = 20 log • (0.7/VN • √5MHz) IC = ±5mA, RE = 100Ω, RC = 1kΩ RC = 40Ω, RE = 100Ω VIN = ±3V IQ = ±17mA RE = 100Ω, RC = 40Ω RE = 100Ω, RC = 40Ω VIN = ±4V VIN = ±2.5V RE = 100Ω RE = 50kΩ IQ = ±17mA RE = 50kΩ, RC = 1kΩ RE = 50kΩ, RC = 40Ω RQ = 750Ω, RE = 50kΩ, RC = 1kΩ, Both Channels Enabled RQ = 750Ω, RE = 50kΩ, RC = 1kΩ, Both Channels Disabled Programmable RQ = 3kΩ to 30Ω Ambient Temperature Output Impedance, rE POWER SUPPLY Rated Voltage Derated Performance Positive Quiescent Current for both OTAs(4) Positive Quiescent Current for both OTAs(4) Quiescent Current Range TEMPERATURE RANGE Specification Thermal Resistance, θJA AP AU +17 +4 ±3 –40 90 100 ±65 +85 mA °C °C/W °C/W NOTES: (1) Characterization sample. (2) “Typical Values” are Mean values. The average of the two amplifiers is used for amplifier specific parameters. (3) “Min” and “Max” Values are mean ±3 Standard Deviations. Worst case of the two amplifiers (Mean ±3 Standard Deviations) is used for amplifier specific parameters. (4) I–Q typically 2mA less than I+Q due to OTA C-Output Bias Current and TTL Select Circuit Current. The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes no responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant any BURR-BROWN product for use in life support devices and/or systems. OPA2662 2 SPECIFICATIONS ELECTRICAL AC-SPECIFICATION (CONT) Typical at VCC = ±5VDC, R Q = 750Ω, IC = ±37.5mA (VIN = 2.5Vpp, RE = 100Ω), IC = ±75mA (VIN = 2.5Vpp, RE = 50Ω), RSOURCE = 50Ω, and TA = +25° C, unless otherwise noted. OPA2662AP, AU PARAMETER FREQUENCY DOMAIN LARGE SIGNAL BANDWIDTH IC = ±37.5mA IC = ±75mA IC = ±37.5mA (Optimized) IC = ±75mA (Optimized) GROUP DELAY TIME Measured Input to Output (Demo Board Used) HARMONIC DISTORTION Second Harmonic Third Harmonic Second Harmonic Third Harmonic Second Harmonic Third Harmonic Second Harmonic Third Harmonic Second Harmonic Third Harmonic Second Harmonic Third Harmonic CROSSTALK RE = 100Ω, RC = 50Ω RE = 100Ω, RC = 25Ω RE = 100Ω, RC = 50Ω, CE = 5.6pF RE = 100Ω, RC = 25Ω, CE = 5.6pF RE = 100Ω, RC = 50Ω B to E B to C f = 10MHz, IC = ±37.5mA f = 10MHz, IC = ±75mA f = 30MHz, IC = ±37.5mA f = 30MHz, IC = ±75mA f = 50MHz, IC = ±37.5mA f = 50MHz, IC = ±75mA Typical Curve Number 3 IC = ±37.5mA, f = 30MHz IC = ±75mA, f = 30MHz RE = 100Ω, f = 30MHz RE = 50Ω, f = 30MHz 10% to 90% 75mA Step IC 150mA Step IC IC = 75mA IC = 150mA 150 200 370 250 1.2 2.5 –31 –37 –33 –32 –29 –32 –30 –25 –31 –30 –28 –23 –51 –56 –90 –90 MHz MHz MHz MHz ns ns dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dBc dB dB dB dB CONDITIONS MIN TYP MAX UNITS FEEDTHROUGH Off Isolation TIME DOMAIN Rise Time Slew Rate 2 2.6 37.5 58 ns ns mA/ns mA/ns CHANNEL SELECTION OPA2662AP, AU PARAMETER ENABLE INPUTS Logic 1 Voltage Logic 0 Voltage Logic 1 Current Logic 0 Current SWITCHING CHARACTERISTICS EN to Channel ON Time EN to Channel OFF Time Switching Transient, Positive Switching Transient, Negative CONDITIONS MIN 2 0 0.8 –1 TYP MAX VCC + 0.6 0.8 10 UNITS V V µA µA ns ns mV mV VSEL = 2.0V to 5V VSEL = 0V to 0.8V IC = 150mAp-p, f = 5MHz 90% Point of VO = 1Vp-p 10% Point of VO = 1Vp-p (Measured While Switching Between the Grounded Channels) 1.1 0.05 30 200 30 –80 3 OPA2662 SPECIFICATIONS (CONT) ELECTRICAL (Full Temperature Range –40°C to +85°C) At VCC = ±5VDC, RQ = 750Ω, TA = TMIN to T MAX, unless otherwise noted, and configured as noted under “CONDITIONS”. OPA2662AP, AU PARAMETER OTA INPUT OFFSET VOLTAGE Initial Matching OTA INPUT BIAS CURRENT Initial Matching OTA TRANSCONDUCTANCE Transconductance OTA C-RATED OUTPUT Output Voltage Compliance POWER SUPPLY Positive Quiescent Current for both OTAs(4) CONDITIONS RE = 50kΩ, RC = 40Ω 12 2 RE = 100Ω, RC = 40Ω –1.9 –1.2 IC = 75mA, RE = 0 IC = ±5mA, RE = 100Ω, RC = 16Ω RQ = 750Ω, RE = 50kΩ, RC = 1kΩ, Both Channels Selected 580 ±3.2 +8 +17 +25 1 0.2 5.9 1.2 610 MIN TYP MAX ±36 ±7.2 UNITS mV mV µA µA mA/V V mA PIN CONFIGURATION Top View SOL-16/DIP ABSOLUTE MAXIMUM RATINGS Power Supply Voltage ........................................................................ ±6V Input Voltage(1) .................................................................. ±VCC to ±0.7V Operating Temperature ................................................... –40° C to +85°C Storage Temperature ..................................................... –40°C to +125°C Junction Temperature .................................................................... +175°C Lead Temperature (soldering, 10s) ............................................... +300°C Digital Input Voltages (EN1, EN2) ............................... –0.5 to +VCC +0.7V NOTE: (1) Inputs are internally diode-clamped to ±VCC. +VCC B1 EN1 GND 1 16 +VCCOUT 15 E1 OTA1 Logic 14 C1 13 NC 12 NC Logic 11 C2 10 E2 9 OPA2662 –VCCOUT 2 3 4 PTAT Supply PACKAGE/ORDERING INFORMATION PACKAGE DRAWING NUMBER(1) 180 211 TEMPERATURE RANGE –40°C to +85°C –40°C to +85°C IQ Adjust EN2 B2 –VCC 5 PRODUCT OPA2662AP OPA2662AU PACKAGE 16-Pin Plastic DIP SOL-16 Surface Mount 6 OTA2 7 NOTE: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. 8 ELECTROSTATIC DISCHARGE SENSITIVITY Any integrated circuit can be damaged by ESD. Burr-Brown recommends that all integrated circuits be handled with appropriate precautions. ESD can cause damage ranging 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 published specifications. Burr-Brown’s standard ESD test method consists of five 1000V positive and negative discharges (100pF in series with 1.5kΩ) applied to each pin. OPA2662 4 TYPICAL PERFORMANCE CURVES At VCC = ±5V, RQ = 750Ω, and TA = +25°C, unless otherwise specified. OTA B TO E-INPUT OFFSET VOLTAGE vs TEMPERATURE 15 OTA B-INPUT RESISTANCE vs TOTAL QUIESCENT CURRENT 18 16 14 12 10 8 6 4 2 0 100 13 12 11 10 9 8 –50 RE = 50kΩ RC = 40Ω –25 0 25 50 75 OTA B-Input Resistance (MΩ) 14 Input Offset Voltage (mV) 7 12 17 22 27 32 37 42 47 Temperature (°C) Total Quiescent Current, IQ (±mA) OTA C-OUTPUT BIAS CURRENT vs TEMPERAURE 0.70 0.65 Output Bias Current (mA) OTA B-INPUT BIAS CURRENT vs TEMPERATURE 1.5 0.60 0.55 0.50 0.45 0.40 0.35 0.30 –50 –25 0 25 50 75 100 Temperature (°C) B-Input Bias Current (µA) 1.3 1.1 0.9 0.7 –50 –25 0 25 50 75 100 Temperature (C°) OTA E-OUTPUT RESISTANCE vs TOTAL QUIESCENT CURRENT 50 9 45 40 35 30 25 20 15 10 5 0 7 12 17 22 27 32 37 42 47 Total Quiescent Current, IQ (±mA) OTA C-OUTPUT RESISTANCE vs TOTAL QUIESCENT CURRENT OTA C-Output Resistance, rC (kΩ) OTA E-Output Resistance rE (Ω) 8 7 6 5 4 3 2 1 0 7 12 17 22 27 32 37 42 47 Total Quiescent Current, IQ (±mA) 5 OPA2662 TYPICAL PERFORMANCE CURVES At VCC = ±5V, RQ = 750Ω, and TA = +25° C, unless otherwise specified. (CONT) TOTAL QUIESCENT CURRENT vs RQ 70 Total Quiescent Current, IQ (±mA) QUIESCENT CURRENT CHANGE vs TEMPERATURE 24 22 Quiescent Current (mA) 60 50 40 30 20 10 0 10 100 1k 10k RQ - Resistor Value (Ω) 20 18 16 14 12 10 –60 –40 –20 0 20 40 60 80 100 Typical Temperature (°C) OTA TRANSFER CHARACTERISTICS vs RE 120 RE = 25Ω OTA C-Output Current (mA) OTA C-Output Current (mA) IC/IE TRANSFER CURVE 100 75 50 25 0 –25 –50 –75 –100 RE = 33Ω, RC = 11Ω –25 –20 –15 –10 –5 0 5 10 15 20 25 30 80 40 0 RE = 100Ω –40 –80 –120 –0.95 RC = 10Ω VIN = 1.9Vp-p 0 Input Voltage (V) 0.95 RE = 33Ω RE = 50Ω OTA E-Output Current (mA) TRANSCONDUCTANCE vs VIN vs IQ 700 OTA Transconductance gm (mA/V) OTA C-Output Current (mA) OTA TRANSFER CHARACTERISTICS vs TOTAL QUIESCENT CURRENT 100 80 IQ = ±34mA IQ = ±65mA 600 IQ = 65mA 500 IQ = 34mA 400 300 200 100 0 –200 IQ = 17mA IQ = 8mA 60 40 20 0 –20 –40 –60 –80 –100 –200 –100 0 Input Voltage (mV) 100 RE = 0Ω 200 IQ = ±17mA IQ = ±8mA –150 –100 –50 0 50 100 150 200 Input Voltage (mV) OPA2662 6 TYPICAL PERFORMANCE CURVES (CONT) At VCC = ±5V, RQ = 750Ω, IC = ±37.5mA (RE = 100Ω, VIN = 2.5Vp-p), IC = ±75mA (RE = 50Ω, VIN = 2.5Vp-p), and T AMB = +25°C, unless otherwise noted. BANDWIDTH vs OUTPUT CURRENT 5 80 OPEN-LOOP GAIN vs FREQUENCY IQ = ±17mA 0 IC = ±75mA RC = 15Ω RE = 25Ω IC = ±37.5mA RC = 30Ω RE = 50Ω 60 IQ = ±8mA IQ = ±34mA 40 Test Circuit 50Ω 100Ω DUT 180Ω +1 Gain (dB) –10 Gain (dB) –5 BUF601 50Ω –15 20 50Ω –20 1M 10M Frequency (Hz) 100M 1G 0 100k 300k 1M 3M 10M 30M 100M Frequency (Hz) OTA LARGE SIGNAL PULSE RESPONSE vs OUTPUT CURRENT 2.0 100 OTA LARGE SIGNAL PULSE RESPONSE vs TOTAL QUIESCENT CURRENT 1.0 ICMAX = ±37mA RE = 100Ω ICMAX = ±75mA RE = 50Ω OTA C-Output Current (mA) OTA C-Output Voltage (V) 50 IQ = ±34mA 0 IQ = ±8mA –5 0 –1.0 IQ = ±17mA tRISE = tFALL = 1ns (Generator) 0 50 100 Time (ns) 150 200 IQ = ±17mA RC = 10Ω, RE = 50Ω –100 0 10 20 Time (ns) 30 40 50 –2.0 OTA LARGE SIGNAL PULSE RESPONSE vs OUTPUT VOLTAGE 1.0 RC = 10Ω OPTIMIZED FREQUENCY RESPONSE vs OUTPUT VOLTAGE 20 6Vp-p OTA C-Output Voltage (V) 0.5 0 Gain (dBm) RC = 30Ω 3Vp-p –20 Test Circuit VIN 100Ω 1.4Vp-p 0.6Vp-p 0 VOUT –0.5 VIN = 2.7Vp-p 100Ω Test Circuit RC 12Ω VOUT 50Ω –40 100Ω RE 6.8pF CE 50Ω 50Ω –1.0 0 50 100 150 200 –60 0.1M IQ = ±17mA 10M Frequency (Hz) 100M 1G 1M Time (ns) 7 OPA2662 TYPICAL PERFORMANCE CURVES tOFF Worst Case EN-TIME (CONT) VCC = ±5V, RQ = 750Ω, IC = ±37.5mA (RE = 100Ω, VIN = 2.5Vp-p), IC = ±75mA (RE = 50Ω, VIN = 2.5Vp-p), and TA = +25°C, unless otherwise specified. SWITCHING TRANSIENT 250 OTA C-Output Current (mA) 4 2 200 2 0 –2 –4 –75 0 0 100 50 0 –50 –100 fIN = 5MHz 0 tON 250 500 Time (ns) Both Inputs Connected with 150Ω to GND 0 250 –150 500 Time (ns) CROSSTALK vs FREQUENCY 20 0 Off Isolation (dB) OFF ISOLATION vs FREQUENCY 20 0 VIN Crosstalk (dB) VIN –20 –40 3 –60 –80 –100 300k 1 2 EN1 VIN CURVE EN1 EN2 1 1 1 2 1 0 EN2 3 0 1 C1 100Ω 50Ω B1 IC1 = 150mAp-p OTA1 E1 C2 OTA2 E2 OPA2662 50Ω 50Ω VOUT 50Ω –20 –40 –60 –80 –100 300k 100Ω B2 1M 10M Frequency (Hz) 100M 1G 1M 10M Frequency (Hz) 100M 1G HARMONIC DISTORTION vs FREQUENCY –20 OTA C-Output Current (mA) OTA TRANSFER CHARACTERISTICS 80 60 40 20 0 –20 –40 –60 –80 –VIN IQ = ±34mA IQ = ±65mA IQ = ±8mA IQ = ±17mA Harmonic Distortion (dBc) –25 2nd Harmonic –30 –35 –40 –45 –50 1.0M 3rd Harmonic IQ = ±17mA RE = 100Ω RC = 50Ω IC = 75mAp-p 3.0M 10M Frequency (Hz) 30M 100M 0 Variable Input Voltage (mV) for ±75mA Collector Current at the End Points +VIN OPA2662 8 Output Voltage (mV) 4 75 150 EN Voltage (V) EN Voltage (V) TYPICAL PERFORMANCE CURVES (CONT) At VCC = ±5V, RQ = 750Ω, (RE = 100Ω, VIN = 2.5Vp-p), IC = ±75mA (RE = 50Ω, VIN = 2.5Vp-p), and TA = +25°C, unless otherwise specified. OTA SPECTRAL NOISE DENSITY –124 140 124 BUFFER SPECTRAL NOISE DENSITY 140 OTA Noise (dBm/√ Hz) OTA Noise (nV/√ Hz) Test Circuit DUT + V N –144 150Ω 14 IQ = ±17mA 4.4 –144 – 50Ω IQ = ±34mA 14 –154 IQ = ±34mA –164 100 IQ = ±8mA –154 150Ω VN 4.4 IQ = ±17mA IQ = ±8mA 1.4 100 1k 10k Frequency (Hz) 100k 1M 1k 10k Frequency (Hz) 100k 1.4 1M –164 BUFFER TRANSFER FUNCTION, B to E 4 3 Buffer Output Voltage (V) BUFFER OUTPUT GAIN ERROR, B to E 50 45 40 –40°C RE = 100Ω IQ = ±17mA 2 1 0 –1 –2 –3 –4 –5 –4 –3 –2 –1 0 1 2 3 4 5 Input Voltage (V) Gain Error (%) 35 30 25 20 15 10 5 0 –5 –4 –3 –2 –1 0 1 2 3 4 5 Input Voltage (V) 85°C OTA E-OUTPUT SMALL SIGNAL PULSE RESPONSE 150 100 Output Voltage (mV) OTA E-OUTPUT LARGE SIGNAL PULSE RESPONSE 4 50 0 –50 –100 IQ = ±17mA, tRISE = tFALL = 1ns (Generator), RE = 100Ω –150 0 20 40 60 Time (ns) 80 100 120 Output Voltage (V) 2 0 –2 IQ = ±17mA, tRISE = tFALL = 1ns (Generator), RE = 100Ω –4 0 20 40 60 Time (ns) 80 100 120 9 OPA2662 Buffer Noise (nV/√ Hz) –134 44 Buffer Noise (dBm/√ Hz) –134 44 APPLICATION INFORMATION The OPA2662 typically operates from ±5V power supplies (±6V maximum). Do not attempt to operate with larger power supply voltages or permanent damage may occur. All inputs of the OPA2662 are protected by internal diode clamps, as shown in the simplified schematic in Figure 1. These protection diodes can safely, continuously conduct 10mA (30mA peak). The input signal current must be limited if input voltages can exceed the power supply voltages by 0.7V, as can occur when power supplies are switched off and a signal source is still present. The buffer outputs E1 and E2 are not current-limited or protected. If these outputs are shorted to ground, high currents could flow. Momentary shorts to ground (a few seconds) should be avoided, but are unlikely to cause permanent damage. DISCUSSION OF PERFORMANCE OTA The two OTA sections of the OPA2662 are versatile driver devices for wide-bandwidth systems. Applications best suited to this new circuit technology are those where the output signal is current rather than voltage. Such applications include driving LEDs, laser diodes, tuning coils, and driver transformers. The OPA2662 is also an excellent choice to drive the video heads of analog or digital video tape recorders in broadcast and HDTV-quality or video heads of highdensity data recorders. The symbol for the OTA sections is similar to that of a bipolar transistor. Application circuits for the OTA look and operate much like transistor circuits—the bipolar transistor, too, is a voltage-controlled current source. The three OTA terminals are labelled; base (B), emitter (E) and collector (C), calling attention to its similarity to a transistor. The OTA sections can be viewed as wide-band, voltage-controlled, bipolar current sources. The collector current of each OTA is controlled by the differential voltage between the high-impedance base and low-impedance emitter. If a current flows at the emitter, then the current mirror reflects this current to the high-impedance collector by a fixed ratio of three. Thus, the collector is determined by the product of the base-emitter voltage times the transconductance times the current mirror factor. The typical performance curves illustrate the OTA open-loop transfer characteristic. Due to the PTAT (Proportional to Absolute Temperature) biasing, the transconductance is constant vs temperature and can be adjusted by an external resistor. The typical performance curves show the transfer characteristic for various quiescent currents. While similar to that of a transistor, this characteristic has one essential difference, as can be seen in the performance curve: the (sense) of the C output current. This current flows out of the C terminal for positive B-to-E input voltage and into for negative. The OTAs offer many advantages over discrete transistors. First of all, they are self-biased and bipolar. The output current is zero-for-zero differential input voltage. AC inputs centered at zero produce an output current that is bipolar and centered at zero. The self-biased OTAs simplify the design process and reduce the number of components. It is far more linear than a transistor. The transconductance of a transistor is proportional to its collector current. But since the collector current is dependent upon the signal, it and the transconductance are fundamentally nonlinear. Like transistor circuits, OTA circuits may also use emitter degeneration +VCC (1) +VCCOUT (16) +VCCOUT (16) x1 x3 EN (3,6) B +1 (2,7) EN (3,6) E (10,15) C Control (11,14) (4) Bias Circuitry B (2,7) E (10,15) IE C (11,14) 3 x IE OTA (9) –VCCOUT x1 (8) –VCC (9) –VCCOUT x3 IQ Adjust (5) RQ (ext.) RQ = 750Ω sets IQ to ±17mA for both OTAs. FIGURE 1. Simplified Block and Circuit Diagram. OPA2662 10 to reduce the effect that offset voltages and currents might otherwise have on the DC operating point of the OTA. The E degeneration resistor may be bypassed by a capacitor to maintain high AC gain. Other cases may require a capacitor with less value to optimize high-frequency performance. The transconductance of the OTA with degeneration can be calculated by: IC C B rE E IE RE 84Ω –3 –2.5 –2 –1.5 –1 I (mA) 70 60 50 40 30 20 IE IC gm' = 1 1 gm + R E 1 ; gm = r E 120 rE + RE (Ω) 100 80 60 RE + rE (IC = ±37.5mA) RE + rE (IC = ±75mA) gm' (IC = ±75mA) 120 100 80 60 40 20 IC ≈ 3 • V IN 3 • V IN ; RE ≈ – rE rE + RE IC 40 20 0 gm' (IC = ±37.5mA) 0 ±0.5 ±1 ±1.5 ±2 ±2.5 ±3 ±3.5 I (mA) IC C 60 B rE E IE RE 33Ω 50 40 30 20 IE 70 IC 0 ±4 Maximum Input Voltage (V) FIGURE 4. RE + rE Selection Curve. DISTORTION The OPA2662’s harmonic distortion characteristics into a 50Ω load are shown vs frequency in the typical performance curves for a total quiescent current of ±17mA for both OTAs, which equals to ±8.5mA for each of them. 1 1.25 VIN (V) –1.25 –1 –0.75 –0.5 0.25 0.5 0.75 –10 –20 –30 –40 –50 –60 –70 The harmonic distortion performance is greatly affected by the applied quiescent current. In order to demonstrate this behavior Figure 5 illustrates the harmonic distortion performance vs frequency for a low quiescent current of ±8mA, for a medium of ±17mA and for a high of ±34mA. It can be seen that the harmonic distortion decreases with all increasing quiescent current. The same effect is expressed in other ways by the OTA transfer characteristics for different IQs in the typical performance curves. ICIC 3 •3IE IE ≈• rE E aries vsvs IQ r v varies IQ IQQ = 17mA I = ± ±17mA FIGURE 2. OTA Transfer Characteristic, RE = 33Ω. 11 OPA2662 Transconductance gm' (mA/V) In application circuits, the resistor RE between the E-output and ground is used to set the OTA transfer characteristic. The input voltage is transferred with a voltage gain of 1V/V to the E-output. According to the E-output impedance and the RE resistor size, a certain current flows to ground. As mentioned before this current is reflected by the current mirror to the high impedance collector output by a fixed ratio of three. Figure 2 and Figure 3 show the OTA transfer characteristic for a RE = 33Ω and RE = 84Ω, which equal to voltage-tocurrent conversion factors (transconductance) of ±75mA/V and ±25mA/V. The limitation for this transconductance adjustment is the maximum E-output current of ±25mA. The achievable transconductance and the corresponding minimum RE versus the input voltage shows Figure 4. The area left to the RE + rE curve can be used and results in a transconductance below the gm’ curve. The variation of rE vs total quiescent current is shown in the typical performance curve section. 0.5 –10 –20 –30 –40 –50 –60 –70 1 1.5 2 2.5 3 VIN (V) IC 3 • IE rE varies vs IQ IQ = ±17mA FIGURE 3. OTA Transfer Characteristic, RE = 84Ω. 160 IE MAX = 25mA 140 160 140 HARMONIC DISTORTION vs TOTAL QUIESCENT CURRENT –20 2nd, 8mA Harmonic Distortion (dBc) 3rd, 8mA –30 3rd, 17mA –40 2nd, 17mA 2nd, 34mA –50 3rd, 34mA –60 1.0M 200ns at full output power (IOUT = ±75mA). This enable feature allows multiplexing and demultiplexing, or a shutdown mode, when the device is not in use. If the EN-input is connected to ground or a digital “Low” is applied to it, the collector (C) and emitter (E) pins are switched in the highimpedance mode. When the EN-input is connected to +5V (+VCC) or a digital “High” is applied to it, the corresponding OTA operates at the adjusted quiescent current. The initial setting for the enable pins is that they are connected to the positive supply as shown in Figure 6. THERMAL CONSIDERATIONS The performance of the OPA2662 is dependent on the total quiescent current which can be externally adjusted over a wide range. As shown later, the distortion will reduce when setting the OTAs for higher quiescent current. For a reliable operation, some thermal considerations should be made. The total power dissipation consists of two separate terms: a) the quiescent power dissipation, PDQ + – P DQ = + V CC • I Q + V CC • I Q 3.0M 10M Frequency (Hz) 30M 100M FIGURE 5. Harmonic Distortion. BASIC CONNECTIONS Shown in Figure 6 are the basic connections for the OPA2662’s standard operation. Most of these connections are not shown in subsequent circuit diagrams for better clarification. Power supply bypass capacitors should be located as close as possible to the device pins. Solid tantalum capacitors are generally the better choice. For further details see the “Circuit Layout” section. ENABLE INPUTS Switching stages compatible to TTL logic levels are provided for each OTA to switch the corresponding voltagecontrolled current source on within 30ns, and off within (1) b) the power dissipation in the output transistors, PDO P DO = ( V OUT – V CC ) • I OUT (2) Equations 1 and 2 can be used in conjunction with the OPA2662’s absolute maximum rating of the junction temperature for a save operation. TJ = TA + (PDQ + PDO) • θJA (3) + 2.2µF 10nF 470pF +5V 100Ω VIN1 +VCC B1 EN1 GND 1 16 +VCCOUT 50Ω 2 OTA1 Logic 4 PTAT Supply 5 Logic 6 OTA2 15 E1 RE1 C1 NC IOUT1 3 14 13 IQ Adjust RQ(1) 100Ω VIN2 –5V B2 EN2 12 NC IOUT2 50Ω RE2 –VCC OUT 11 C2 E2 7 10 8 –VCC OPA2662 9 NOTE: (1) RQ = 750Ω set roughly, IQ = ±17mA. + 2.2µF 10nF 470pF FIGURE 6. Basic Connections. OPA2662 12 QUIESCENT CURRENT CONTROL The quiescent current of the OPA2662 can be varied by connecting a user selectable external resistor, RQ, between pin 5 and –VCC. The quiescent current affects the operating currents of both OTA sections simultaneously, controlling the bandwidth and the AC-behavior as well as the transconductance. The typical performance curves illustrate the relationship of the quiescent current versus the RQ and the transconductance, gM. The OPA2662 is specified at a typical quiescent current of ±17mA. This is set by a resistor RQ of 750Ω at 25°C ambient temperature. The useful range for the IQ is from ±3mA to ±65 mA (see Figure 7). The application circuits do not always show the resistor RQ, but it is required for proper operation. With a fixed resistor, the quiescent current increases with increasing temperature, keeping the transconductance and AC-behavior constant. Figure 7 shows the internal current source circuitry. A resistor with a value of 150Ω is used to limit the current if pin 5 is shorted to –VCC. This resistor has a relative accuracy of ±25% which causes an increasing deviation from the typical RQ vs IQ curve at decreasing RQ values. CIRCUIT LAYOUT The high-frequency performance of the power operational transconductance amplifier OPA2662 can be greatly affected by the physical layout of the printed circuit board. The following tips are offered as suggestions, not as absolute musts. Oscillations, ringing, poor bandwidth and settling, and peaking are all typical problems that plague high-speed components when they are used incorrectly. • Bypass power supplies very close to the device pins. Use tantalum chip capacitors (approximately 2.2µF); a parallel 470pF ceramic and a 10µF chip capacitor may be added if desired. Surface-mount types are recommended because of their low lead inductance. • PC board traces for power lines should be wide to reduce impedance or inductance. • Make short, low-inductance traces. The entire physical circuit should be as small as possible. • Use a low-impedance ground plane on the component side to ensure that low-impedance ground is available throughout the layout. • Do not extend the ground plane under high-impedance nodes sensitive to stray capacitances such as the amplifier’s input terminals. OPA2662 • Sockets are not recommended because they add significant inductance and parasitic capacitance. If sockets must be used, consider using zero-profile solderless sockets. • Use low-inductance, surface-mounted components. Circuits using all surface-mount components with the OPA2662 will offer the best AC performance. • A resistor (100Ω to 250Ω) in series with the highimpedance inputs is recommended to reduce peaking. • Plug-in prototype boards and wire-wrap boards will not function well. A clean layout using RF techniques is essential—there are no shortcuts. 50kΩ 150Ω ±25% 5 RQ –VCC TOTAL QUIESCENT CURRENT vs RQ 70 Total Quiescent Current, IQ (±mA) 60 50 40 30 20 10 0 10 100 1k 10k RQ - Resistor Value (Ω) 8 Typical • Some applications may require a limitation for the maximum output current to flow. This can be achieved by adding a resistor (about 10Ω) between supply lines 1 and 16, and, 8 and 9 (see also Figure 8). The tradeoff of this technique is a reduced output voltage swing. This is due to the voltage drop across the resistors caused by both the collector and the emitter currents. FIGURE 7. Quiescent Current Setting. 13 OPA2662 +5V Rt1 150Ω R1 B1 R2 Rb1 100Ω 51Ω E1 Re1 Re2(1) Ce1(1) Pos +5V C1 2.2µF GND +5V Rt2 R3 100Ω B2 R4 100Ω 100Ω Re3 51Ω E2 Re4(1) Ce2(1) 150Ω 7 10 OTA2 11 RC4(1) RC3 C2 0Ω CC2(1) RQ 750Ω 5 TTL2 Neg –5V Rb2 Rn1 10Ω 9 8 C4 2.2µF C5 10nF C6(1) C2 10nF C3(1) 4 1 100Ω 100Ω 2 15 OTA1 14 Rc1 C1 0Ω RC2(1) CC1(1) Rp1 10Ω 16 TTL1 NOTE: (1) Not assembled. FIGURE 8. Evaluation Circuit Schematic. Silk Screen Component Side Solder Side FIGURE 9. Evaluation Circuit Silkscreen and Board Layouts. OPA2662 14 TYPICAL APPLICATIONS VOUT 14 100Ω VIN 2 OPA2662 15 150Ω 10 100Ω 11 7 50Ω 50Ω VOUT FIGURE 10. Single Ended-to-Differential Line Driver. RQ –VCC 100Ω VIN1 RB1 5 OPA2662 IOUT 14 2 EN1 3 4 100Ω VIN2 EN2 RB2 RQ –VCC 100Ω VIN3 RB3 2 7 6 5 15 11 50Ω 10 14 50Ω EN3 3 4 100Ω VIN4 EN4 OPA2662 7 15 11 50Ω 150Ω 150Ω 150Ω RB4 6 12 16 8 CS1 5 Y3 13 Y2 74HC237 CS2 A2 A1 A0 14 Y1 Y0 LE 150Ω 4 5 10 50Ω FIGURE 11. Current Distribution Multiplexer. 15 OPA2662 +5V Application Specific +VCC +VCCOUT 2N3906 1 RQ –VCC IQ 5 100Ω B 1 VIN1 2 GND 4 VIN2 100Ω B 2 7 EN1 EN 3 EN2 OPA2662 6 8 9 E2 10 –5V EN2 +VCC +VCCOUT 1 RQ 16 C1 14 RB1 3 100Ω 2 15 E1 4 75Ω C2 11 7 E2 10 6 OPA2662 8 9 225Ω –VCC –VCCOUT VE = ±1V VE = ±1V 225Ω VOUT = ±1V 75Ω IOUT = ±13mA 75Ω VOUT = ±1V 16 C1 14 IOUT2 15 E1 C2 11 VIN2 IOUT1 IBIAS IBIAS OPA602 –VCC EN1 VIN1 5 LASER DIODE RB2 100Ω 75Ω –VCC –VCCOUT 50Ω 50Ω FIGURE 12. Laser Diode Driver. FIGURE 13. Two-Channel Current Output Driver. RQ –VCC EN1 5 IQ 3 C1 14 33pF RB1 100Ω B1 2 4 E1 15 C2 47Ω 68Ω 33pF 75Ω VOUT1 75Ω VIN RB2 100Ω EN2 11 B2 7 E2 10 6 OPA2662 75Ω 47Ω 68Ω 75Ω VOUT2 FIGURE 14. Direct Feedback Buffer and 1 to 2 Demultiplexer. OPA2662 16 +VCC +VCCOUT 1 RQ –VCC RB1 100Ω Q ±1V Data Equalization Q RB2 100Ω TTL Record/Play Selection 5 IQ 2 B1 16 C1 14 Voltage compliance across the load: 8Vp-p IOUT = ±75mA E1 15 39Ω ROG 10 E2 Playback Amplifier 3 EN1 GND 4 6 EN2 7 B2 C2 OPA2662 8 9 11 –VCC –VCCOUT FIGURE 15. Analog-to-Digital Video Tape Record Amplifier. +80V 430Ω 75 BFQ262 14 100Ω 2 15 1 100Ω 10 7 11 6 OPA2662 1.5kΩ 200Ω 10 t EN1 EN2 t 10pF –5V FIGURE 16. Cascode Stage Driver. C 100Ω VIN 50Ω 1/2 OPA2662 B E RE 100Ω CE 6.8pF 50Ω VOUT 50Ω The precise pulse response and the high slew rate enables the OPA2662 to be used in digital communication systems. Figure 16 shows the output amplifier for a high-speed data transmission system up to 440Mbit/s. The current source output drives directly a 50Ω coax cable and guarantees a 1V voltage drop over the termination resistor at the end of the cable. The input voltage to output voltage conversion factor is set by RE. CE compensates the stray capacitance at the collector output. The generator rise and fall time equals to 1.19ns and the OPA2662 slightly increases the rise and fall time to 1.26ns. FIGURE 17. Driver Amplifier for a Digital 440Mbit/s Transmission System. 17 OPA2662 600 Output 400 Voltage (mV) 200 0 –200 –400 –600 0 IQ = ±17mA RE = 100Ω CE = 6.8pF RC = 50Ω 2 4 Time (ns) Input 6 8 10 FIGURE 18. Pulse Response of the 400Mbit/s Line Driver. VOUT /VIN 50Ω OPA2662 C1 14 50Ω 50Ω Coax B1 2 E1 15 100Ω Coax C2 11 50Ω 50Ω 50Ω VOUT /VIN 6.8pF 100Ω 7 100Ω B2 3 EN1 6 EN2 E2 10 100Ω T/R Control 6.8pF FIGURE 19. Bidirectional Line Driver. +80V; 60mA to CRT tR = 0.7ns tF = 0.7ns 50Ω 0.46Vp-p 150Ω 7 OPA2662 11 14 1 CR3425 9 12pF tR = 2.4ns tF = 2.15ns 50Vp-p 150Ω 10 2 10nF 15 10Ω 50Ω 220Ω 220Ω 20pF 100pF FIGURE 20. CRT Output Stage Driver for a 1600 x 1200 High-Resolution Graphic Monitor. OPA2662 18