OP496GSZ

Micropower RRIO Operational Amplifiers OP196/OP296/OP496 a FEATURES Rail-to-Rail Input and Output Swing Low Power: 60 ␮A/Amplifier Gain Bandwidth Product: 450 kHz Single-Supply Operation: 3 V to 12 V Low Offset Voltage: 300 ␮V max High Open-Loop Gain: 500 V/mV Unity-Gain Stable No Phase Reversal PIN CONFIGURATIONS 8-Lead Narrow-Body SO NULL 1 8 NC –IN A 2 7 V+ 6 OUT A +IN A 3 OP196 V– 4 5 NULL OUT A 1 –IN A 2 +IN A 3 V– 4 8 V+ OP296 7 OUT B 6 –IN B 5 +IN B NC = NO CONNECT APPLICATIONS Battery Monitoring Sensor Conditioners Portable Power Supply Control Portable Instrumentation 8-Lead TSSOP 1 GENERAL DESCRIPTION 8-Lead Narrow-Body SO OUT A –IN A +IN A V– 8 V+ OUT B –IN B +IN B OP296 4 5 The OP196 family of CBCMOS operational amplifiers features micropower operation and rail-to-rail input and output ranges. The extremely low power requirements and guaranteed operation from 3 V to 12 V make these amplifiers perfectly suited to monitor battery usage and to control battery charging. Their dynamic performance, including 26 nV/√Hz voltage noise density, recommends them for battery-powered audio applications. Capacitive loads to 200 pF are handled without oscillation. The OP196/OP296/OP496 are specified over the extended industrial (–40°C to +125°C) temperature range. 3 V operation is specified over the 0°C to 125°C temperature range. The single OP196 and the dual OP296 are available in 8-lead SOIC and TSSOP packages. The quad OP496 is available in 14-lead SOIC and TSSOP packages. 14-Lead Narrow-Body SO OUT A 1 –IN A 2 +IN A 3 V+ 4 OP496 +IN B 5 –IN B 6 14 OUT D 13 –IN D 12 +IN D 11 V– 10 +IN C 9 –IN C OUT B 7 8 OUT C 14-Lead TSSOP (RU Suffix) 1 OUT A –IN A +IN A V+ +IN B –IN B OUT B 14 OUT D –IN D +IN D V– +IN C –IN C OUT C OP496 7 8 REV. E Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 www.analog.com Fax: 781/461-3113 © 2002-2011 Analog Devices, Inc. OP196/OP296/OP496–SPECIFICATIONS ELECTRICAL SPECIFICATIONS (@ V = 5.0 V, V S CM = 2.5 V, TA = 25ⴗC, unless otherwise noted.) Parameter Symbol Conditions INPUT CHARACTERISTICS Offset Voltage VOS OP196G, OP296G, OP496G –40°C ≤ TA ≤ +125°C OP296H, OP496H –40°C ≤ TA ≤ +125°C –40°C ≤ TA ≤ +125°C Input Bias Current Input Offset Current IB IOS Input Voltage Range VCM Common-Mode Rejection Ratio CMRR Large Signal Voltage Gain AVO Long-Term Offset Voltage VOS Offset Voltage Drift ∆VOS/∆T OUTPUT CHARACTERISTICS Output Voltage Swing High VOH Output Voltage Swing Low VOL Output Current IOUT POWER SUPPLY Power Supply Rejection Ratio Supply Current per Amplifier PSRR ISY Min Typ Max Unit 35 300 650 800 1.2 ± 50 ±8 ± 20 µV µV µV mV nA nA nA 5.0 V ± 10 ± 1.5 –40°C ≤ TA ≤ +125°C 0 0 V ≤ VCM ≤ 5.0 V, –40°C ≤ TA ≤ +125°C RL = 100 kΩ, 0.30 V ≤ VOUT ≤ 4.7 V, –40°C ≤ TA ≤ +125°C G Grade, Note 1 H Grade, Note 1 G Grade, Note 2 H Grade, Note 2 IL = + 100 µA IL = 1 mA IL = 2 mA IL = – 100 μA IL = –1 mA IL = –2 mA ± 2.5 V ≤ VS ≤ ± 6 V, –40°C ≤ TA ≤ +125°C VOUT = 2.5 V, RL = ∞ –40°C ≤ TA ≤ +125°C 65 150 dB 200 1.5 2 V/mV µV mV µV/°C µV/°C 4.92 4.56 4.1 36 350 750 ±4 V V V mV mV mV mA 550 1 4.85 4.30 70 550 85 45 60 80 dB µA µA DYNAMIC PERFORMANCE Slew Rate Gain Bandwidth Product Phase Margin SR GBP øm RL = 100 kΩ 0.3 350 47 V/µs kHz Degrees NOISE PERFORMANCE Voltage Noise Voltage Noise Density Current Noise Density en p-p en in 0.1 Hz to 10 Hz f = 1 kHz f = 1 kHz 0.8 26 0.19 µV p-p nV/√Hz pA/√Hz NOTES 1 Long-term offset voltage is guaranteed by a 1,000 hour life test performed on three independent lots at 12 5°C, with an LTPD of 1.3. 2 Offset voltage drift is the average of the –40°C to +25°C delta and the +25°C to +125°C delta. Specifications subject to change without notice. –2– REV. E OP196/OP296/OP496 ELECTRICAL SPECIFICATIONS (@ VS = 3.0 V, VCM = 1.5 V, TA = 25ⴗC, unless otherwise noted.) Parameter Symbol Conditions INPUT CHARACTERISTICS Offset Voltage VOS OP196G, OP296G, OP496G 0°C ≤ TA ≤ 125°C OP296H, OP496H 0°C ≤ TA ≤ 125°C Input Bias Current Input Offset Current IB IOS Input Voltage Range VCM Common-Mode Rejection Ratio CMRR Large Signal Voltage Gain Long-Term Offset Voltage AVO VOS Offset Voltage Drift ∆VOS/∆T Min Typ Max Unit 35 300 650 800 1.2 ± 50 ±8 µV µV µV mV nA nA 3.0 V 550 1 dB V/mV µV mV µV/°C µV/°C ± 10 ±1 0 0 V ≤ VCM ≤ 3.0 V, 0°C ≤ TA ≤ 125°C RL = 100 kΩ G Grade, Note 1 H Grade, Note 1 G Grade, Note 2 H Grade, Note 2 60 80 200 1.5 2 OUTPUT CHARACTERISTICS Output Voltage Swing High Output Voltage Swing Low VOH VOL IL = 100 µA IL = –100 µA POWER SUPPLY Supply Current per Amplifier ISY VOUT = 1.5 V, RL = ∞ 0°C ≤ TA ≤ 125°C DYNAMIC PERFORMANCE Slew Rate Gain Bandwidth Product Phase Margin SR GBP øm RL = 100 kΩ 0.25 350 45 V/µs kHz Degrees NOISE PERFORMANCE Voltage Noise Voltage Noise Density Current Noise Density en p-p en in 0.1 Hz to 10 Hz f = 1 kHz f = 1 kHz 0.8 26 0.19 µV p-p nV/√Hz pA/√Hz 2.85 40 NOTES 1 Long-term offset voltage is guaranteed by a 1,000 hour life test performed on three independent lots at 12 5°C, with an LTPD of 1.3. 2 Offset voltage drift is the average of the 0°C to 25°C delta and the 25°C to 125°C delta. Specifications subject to change without notice. REV. E –3– 70 V mV 60 80 µA µA OP196/OP296/OP496 ELECTRICAL SPECIFICATIONS (@ V = 12.0 V, V S CM = 6 V, TA = 25ⴗC, unless otherwise noted.) Parameter Symbol Conditions INPUT CHARACTERISTICS Offset Voltage VOS OP196G, OP296G, OP496G 0°C ≤ TA ≤ 125°C OP296H, OP496H 0°C ≤ TA ≤ 125°C –40°C ≤ TA ≤ +125°C Input Bias Current Input Offset Current IB IOS Input Voltage Range VCM Common-Mode Rejection Ratio CMRR Large Signal Voltage Gain Long-Term Offset Voltage AVO VOS Offset Voltage Drift ∆VOS/∆T OUTPUT CHARACTERISTICS Output Voltage Swing High VOH Output Voltage Swing Low VOL Output Current IOUT POWER SUPPLY Supply Current per Amplifier Supply Voltage Range ISY Min Typ Max Unit 35 300 650 800 1.2 ± 50 ±8 ± 15 µV µV µV mV nA nA nA 12 V 550 1 1.5 2 dB V/mV µV mV µV/°C µV/°C ±4 V V mV mV mA ± 10 ±1 –40°C ≤ TA ≤ +125°C 0 0 V ≤ VCM ≤ 12 V, –40°C ≤ TA ≤ +125°C RL = 100 kΩ G Grade, Note 1 H Grade, Note 1 G Grade, Note 2 H Grade, Note 2 IL = 100 µA IL = 1 mA IL = – 100 μA IL = –1 mA 65 300 1000 11.85 11.30 70 550 VOUT = 6 V, RL = ∞ –40°C ≤ TA ≤ +125°C VS 60 80 12 3 µA µA V DYNAMIC PERFORMANCE Slew Rate Gain Bandwidth Product Phase Margin SR GBP øm RL = 100 kΩ 0.3 450 50 V/µs kHz Degrees NOISE PERFORMANCE Voltage Noise Voltage Noise Density Current Noise Density en p-p en in 0.1 Hz to 10 Hz f = 1 kHz f = 1 kHz 0.8 26 0.19 µV p-p nV/√Hz pA/√Hz NOTES 1 Long-term offset voltage is guaranteed by a 1,000 hour life test performed on three independent lots at 12 5°C, with an LTPD of 1.3. 2 Offset voltage drift is the average of the –40°C to +25°C delta and the +25°C to +125°C delta. Specifications subject to change without notice. –4– REV. E OP196/OP296/OP496 ABSOLUTE MAXIMUM RATINGS 1 Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 V Input Voltage2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 V Differential Input Voltage2 . . . . . . . . . . . . . . . . . . . . . . . . 15 V Output Short Circuit Duration . . . . . . . . . . . . . . . . . Indefinite Storage Temperature Range S, RU Package . . . . . . . . . . . . . . . . . . . . –65°C to +150°C Operating Temperature Range OP196G, OP296G, OP496G, H . . . . . . . –40°C to +125°C Junction Temperature Range S, RU Package . . . . . . . . . . . . . . . . . . . –65°C to +150°C Lead Temperature Range (Soldering, 60 sec) . . . . . . . . 300°C Package Type ␪JA3 ␪JC Unit 8-Lead SOIC 8-Lead TSSOP 158 240 43 43 °C/W °C/W 14-Lead SOIC 14-Lead TSSOP 120 180 36 35 °C/W °C/W NOTES 1 Absolute maximum ratings apply to packaged parts, unless otherwise noted. 2 3 For supply voltages less than 15 V, the absolute maximum input voltage is equal to the supply voltage. θJA is specified for the worst case conditions ; θJA is specified for device soldered in circuit board for SOIC and TSSOP packages. CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the OP196/OP296/OP496 feature proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high-energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality. REV. E –5– WARNING! ESD SENSITIVE DEVICE OP196/OP296/OP496–Typical Performance Characteristics 25 250 150 100 0 –250 –200 –150 –100 –50 0 50 100 150 INPUT OFFSET VOLTAGE – ␮V 200 1.0 25 VS = 5V TA = 25ⴗC COUNT = 400 VS = 12V VCM = 6V TA = –40ⴗC TO ⴙ125ⴗC 20 QUANTITY – Amplifiers QUANTITY – Amplifiers –3.0 –2.5 –2.0 –1.5 –1.0 –0.5 0 0.5 INPUT OFFSET DRIFT, TCVOS – ␮V/ⴗC TPC 4. Input Offset Voltage Distribution (TCVOS) 250 150 100 15 10 5 50 0 –250 –200 –150 –100 –50 0 50 100 150 INPUT OFFSET VOLTAGE – ␮V 200 0 –4.0 –3.5 –3.0 –2.5 –2.0 –1.5 –1.0 –0.5 0 0.5 INPUT OFFSET DRIFT, TCVOS – ␮V/ⴗC 250 TPC 2. Input Offset Voltage Distribution 1.0 1.5 TPC 5. Input Offset Voltage Distribution (TCVOS) 250 600 VS = 12V TA = 25ⴗC COUNT = 400 3V INPUT OFFSET VOLTAGE – ␮V QUANTITY – Amplifiers 10 0 –4.0 –3.5 250 TPC 1. Input Offset Voltage Distribution 200 15 5 50 200 VS = 5V VCM = 2.5V TA = –40ⴗC TO ⴙ125ⴗC 20 QUANTITY – Amplifiers QUANTITY – Amplifiers 200 VS = 3V TA = 25ⴗC COUNT = 400 150 100 50 0 –250 –200 –150 –100 –50 0 50 100 150 INPUT OFFSET VOLTAGE – ␮V 400 VS 12V VS 2 VCM = 200 0 –200 200 –400 –75 250 TPC 3. Input Offset Voltage Distribution –50 –25 0 25 50 75 TEMPERATURE – ⴗC 100 125 150 TPC 6. Input Offset Voltage vs. Temperature –6– REV. E OP196/OP296/OP496 25 1000 VS = 5V VCM = 2.5V VS = ⴞ1.5V OUTPUT VOLTAGE – mV INPUT BAIS CURRENT – nA 20 15 10 –50 –25 0 25 50 75 TEMPERATURE – ⴗC 100 125 SINK 10 1 0.001 150 TPC 7. Input Bias Current vs. Temperature 0.01 10 0.1 1 LOAD CURRENT – mA TPC 10. Output Voltage to Supply Rail vs. Load Current 1000 16 VS = ⴞ2.5V OUTPUT VOLTAGE – mV INPUT BIAS CURRENT – nA SOURCE 5 0 –75 12 8 4 2 3 12 5 SUPPLY VOLTAGE – V SOURCE SINK 10 0.01 10 0.1 1 LOAD CURRENT – mA TPC 11. Output Voltage to Supply Rail vs. Load Current 40 30 100 1 0.001 14 TPC 8. Input Bias Current vs. Supply Voltage 1000 VS = ⴞ2.5V TA = 25ⴗC VS = ⴞ6V 20 OUTPUT VOLTAGE – mV INPUT BIAS CURRENT – nA 100 10 0 –10 –20 100 SOURCE SINK 10 –30 –40 0 0.5 1.0 1.5 –2.5 –2.0 –1.5 –1.0 –0.5 COMMON-MODE VOLTAGE – V 2.0 1 0.001 2.5 TPC 9. Input Bias Current vs. Common-Mode Voltage REV. E 0.01 0.1 1 LOAD CURRENT – mA 10 TPC 12. Output Voltage to Supply Rail vs. Load Current –7– OP196/OP296/OP496 4.95 90 I L = 100␮A VS = ⴞ2.5V TA = –40ⴗC 80 70 4.45 I L = 2mA 4.2 VS = 5V 60 GAIN 50 –50 –25 0 25 50 75 TEMPERATURE – ⴗC 100 125 135 0 180 1k 10k FREQUENCY – Hz 100 225 1M 100k 90 VS = ⴞ2.5V TA = 125ⴗC 80 0.60 70 0.50 0.30 0.10 60 GAIN 50 40 0 30 45 90 20 PHASE 135 10 –50 –25 0 25 50 75 TEMPERATURE – ⴗC 180 0 I L = –100␮A 100 125 –10 10 150 TPC 14. Output Voltage Swing vs. Temperature 1k 10k FREQUENCY – Hz 100 PHASE SHIFT – ⴗC I L = –1mA OPEN-LOOP GAIN – dB VOL OUTPUT VOLTAGE – V 10 TPC 16. Open-Loop Gain and Phase vs. Frequency (No Load) VS = 5V 225 1M 100k TPC 17. Open-Loop Gain and Phase vs. Frequency (No Load) 90 950 VS = ⴞ2.5V TA = 25ⴗC 80 VS = 5V 0.3V < VO < 4.7V RL = 100k⍀ 800 70 OPEN-LOOP GAIN – V/mV 60 GAIN 50 40 0 30 45 20 90 PHASE 10 135 0 180 100 1k 10k FREQUENCY – Hz 100k PHASE SHIFT – ⴗC OPEN-LOOP GAIN – dB 90 PHASE 0.80 –10 10 45 –10 10 150 TPC 13. Output Voltage Swing vs. Temperature –75 0 30 20 3.85 3.7 –75 40 PHASE SHIFT – ⴗC I L = 1mA OPEN-LOOP GAIN – dB VOH OUTPUT VOLTAGE – V 4.70 225 1M 650 500 350 200 –75 –50 –25 0 25 50 75 TEMPERATURE – ⴗC 100 125 150 TPC 18. Open-Loop Gain vs. Temperature TPC 15. Open-Loop Gain and Phase vs. Frequency (No Load) –8– REV. E OP196/OP296/OP496 160 600 VS = ⴞ2.5V TA = 25ⴗC ALL CHANNELS 140 VS = 5V OPEN-LOOP GAIN – V/mV 500 120 TA = 25ⴗC 100 80 CMRR – dB 400 300 60 40 200 20 0 100 –20 0 150 100 50 10 LOAD – k⍀ 2 –40 100 1 TPC 19. Open-Loop Gain vs. Resistive Load 10k 100k FREQUENCY – Hz 10M 160 VS = ⴞ2.5V RL = 10k⍀ TA = 25ⴗC 60 50 VS = 5V TA = 25ⴗC 140 120 40 PSRR – dB 100 30 20 10 80 +PSRR 60 40 –PSRR 0 20 –10 0 –20 –20 –30 10 100 1k 10k FREQUENCY – Hz 100k –40 10 1M 100 1k 10k 100k FREQUENCY – Hz 10M 6 1000 VS = ⴞ2.5V VIN = 5V p-p AV = 1 RL = 100k⍀ 900 5 VS = ⴞ2.5V TA = 25ⴗC MAXIMUM OUTPUT SWING – V 800 1M TPC 23. PSRR vs. Frequency TPC 20. Closed-Loop Gain vs. Frequency OUTPUT IMPEDANCE – ⍀ 1M TPC 22. CMRR vs. Frequency 70 CLOSED-LOOP GAIN – dB 1k 700 600 ACL = 10 500 400 ACL = 1 300 200 4 3 2 1 100 0 100 1k 10k FREQUENCY – Hz 100k 0 1k 1M TPC 21. Output Impedance vs. Frequency REV. E 10k 100k FREQUENCY – Hz 1M TPC 24. Maximum Output Swing vs. Frequency –9– OP196/OP296/OP496 90 0.6 CURRENT NOISE DENSITY – pA/ Hz ISY/AMPLIFIER – ␮A 80 70 VS = 12V 60 50 VS = 5V 40 VS = 3V 30 20 –75 –50 –40 –25 0 25 50 75 85 TEMPERATURE – ⴗC VS = ⴞ2.5V TA = 25ⴗC VCM = 0V 0.5 0.4 0.3 0.2 0.1 0 1 100 125 150 TPC 25. Supply Current/Amplifier vs. Temperature 10 1k 100 FREQUENCY – Hz TPC 28. Input Bias Current Noise Density vs. Frequency 10 55 TA = 25ⴗC 8 VS = ⴞ6V 6 TA = 25ⴗC TO 0.1% 50 ⴙOUTPUT SWING INPUT STEP – V ISY/AMPLIFIER – ␮A 4 45 2 0 –2 –4 – OUTPUT SWING 40 –6 –8 35 1 3 5 7 9 11 SUPPLY VOLTAGE – V 12 –10 0 13 5 10 15 20 SETTLING TIME – ␮s 25 30 TPC 29. Settling Time to 0.1% vs. Step Size TPC 26. Supply Current/Amplifier vs. Supply Voltage VOLTAGE NOISE DENSITY – nV/ Hz 80 VS = ⴞ2.5V TA = 25ⴗC VCM = 0V 70 2mV 1s 100 90 60 50 40 30 10 0% 20 VS = ⴞ2.5V AV = 10k en = 0.8␮V p-p 10 0 1 10 100 FREQUENCY – Hz 1k TPC 30. 0.1 Hz to 10 Hz Noise TPC 27. Voltage Noise Density vs. Frequency –10– REV. E OP196/OP296/OP496 100mV 100 90 VS = 2.5V AV = 1 RL = 10k⍀ CL = 100pF TA = 25ⴗC 10 0V 0% 20mV 10 0% 2␮s TPC 33. Large Signal Transient Response VS = ⴞ2.5V RL = 100k⍀ 100 90 100 90 VS = ⴞ2.5V AV = 1 RL = 100k⍀ CL = 100pF TA = 25ⴗC 10 0V 10␮s 1V TPC 31. Small Signal Transient Response 100mV VS = ⴞ2.5V RL = 10k⍀ 100 90 0% 20mV 10 0% 10␮s 1V 2␮s TPC 32. Small Signal Transient Response TPC 34. Large Signal Transient Response CH A: 40.0␮V FS MKR: 36.8␮V/ Hz 5.00␮V/DIV 10Hz 0Hz MKR: 1.00Hz BW: 145mHz TPC 35. 1/f Noise Corner, VS = ± 5 V, AV = 1,000 VCC R1 R2 I1 R7 R6 R8 I4 D3 Q17 D8 QC1 Q4 1x Q2 CF2 Q14 Q8 D5 Q10 Q9 2x OUT CF1 Q13 2x Q21 CC2 1x 1x 1x Q7 Q1 D4 2x Q3 +IN Q12 Q6 Q5 2x Q22 D9 QL1 Q11 I5 Q18 D6 2x QC2 Q19 1x Q23 R5 –IN R3A R3B CC1 R4A R9 I3 I2 Q16 Q15 R4B D7 1.5x D10 1x VEE 1* 5* *OP196 ONLY TPC 36. Simplified Schematic REV. E Q20 –11– OP196/OP296/OP496 The OP196 family of operational amplifiers is comprised of singlesupply, micropower, rail-to-rail input and output amplifiers. Input offset voltage (VOS) is only 300 µV maximum, while the output will deliver ±5 mA to a load. Supply current is only 50 µA, while bandwidth is over 450 kHz and slew rate is 0.3 V/µs. TPC 36 is a simplified schematic of the OP196—it displays the novel circuit design techniques used to achieve this performance. the supply rails. In the circuit of Figure 2, the source amplitude is ± 15 V, while the supply voltage is only ± 5 V. In this case, a 2 kΩ source resistor limits the input current to 5 mA. 5V VOLTAGE – 5V/DIV APPLICATIONS INFORMATION Functional Description Input Overvoltage Protection The OPx96 family of op amps uses a composite PNP/NPN input stage. Transistor Q1 in Figure 36 has a collector-base voltage of 0 V if +IN = VEE. If +IN then exceeds VEE, the junction will be forward biased and large diode currents will flow, which may damage the device. The same situation applies to +IN on the base of transistor Q5 being driven above VCC. Therefore, the inverting and noninverting inputs must not be driven above or below either supply rail unless the input current is limited. Figure 1 shows the input characteristics for the OPx96 family. This photograph was generated with the power supply pins connected to ground and a curve tracer’s collector output drive connected to the input. As shown in the figure, when the input voltage exceeds either supply by more than 0.6 V, internal pn-junctions energize and permit current flow from the inputs to the supplies. If the current is not limited, the amplifier may be damaged. To prevent damage, the input current should be limited to no more than 5 mA. VS = 5V AV = 1 100 90 VIN 0 VOUT 0 10 0% 5V 1ms TIME – 1ns/DIV Figure 2. Output Voltage Phase Reversal Behavior Input Offset Voltage Nulling The OP196 provides two offset adjust terminals that can be used to null the amplifier’s internal VOS. In general, operational amplifier terminals should never be used to adjust system offset voltages. A 100 kΩ potentiometer, connected as shown in Figure 3, is recommended to null the OP196’s offset voltage. Offset nulling does not adversely affect TCVOS performance, providing that the trimming potentiometer temperature coefficient does not exceed ± 100 ppm/°C. V+ OP196 INPUT CURRENT – mA 6 4 7 2 8 6 4 100 90 3 5 1 2 100k⍀ 0 V– –2 –4 10 Figure 3. Offset Nulling Circuit 0% –6 Driving Capacitive Loads –8 –1.5 –1 –0.5 0 0.5 1 1.5 INPUT VOLTAGE – V Figure 1. Input Overvoltage I-V Characteristics of the OPx96 Family OP196 family amplifiers are unconditionally stable with capacitive loads less than 170 pF. When driving large capacitive loads in unity-gain configurations, an in-the-loop compensation technique is recommended, as illustrated in Figure 4. RG Output Phase Reversal RF VIN Some other operational amplifiers designed for single-supply operation exhibit an output voltage phase reversal when their inputs are driven beyond their useful common-mode range. Typically for single-supply bipolar op amps, the negative supply determines the lower limit of their common-mode range. With these common-mode limited devices, external clamping diodes are required to prevent input signal excursions from exceeding the device’s negative supply rail (i.e., GND) and triggering output phase reversal. CF RX OP296 VOUT CL RX = RO RG RF WHERE RO = OPEN-LOOP OUTPUT RESISTANCE CF = The OPx96 family of op amps is free from output phase reversal effects due to its novel input structure. Figure 2 illustrates the performance of the OPx96 op amps when the input is driven beyond the supply rails. As previously mentioned, amplifier input current must be limited if the inputs are driven beyond I+ ( |AICL| ) ( RFR+ RG ) CL RO F Figure 4. In-the-Loop Compensation Technique for Driving Capacitive Loads –12– REV. E OP196/OP296/OP496 same potential and no current flows in R1. Since there is no current flow in R1, the same condition must exist in R2; thus, the output of the circuit tracks the input signal. When the input signal is below 0 V, the output voltage of A1 is forced to 0 V. This condition now forces A2 to operate as an inverting voltage follower because the noninverting terminal of A2 is also at 0 V. The output voltage of VOUTA is then a full-wave rectified version of the input signal. A resistor in series with A1’s noninverting input protects the ESD diodes when the input signal goes below ground. A Micropower False-Ground Generator Some single supply circuits work best when inputs are biased above ground, typically at 1/2 of the supply voltage. In these cases, a false-ground can be created by using a voltage divider buffered by an amplifier. One such circuit is shown in Figure 5. This circuit will generate a false-ground reference at 1/2 of the supply voltage, while drawing only about 55 µA from a 5 V supply. The circuit includes compensation to allow for a 1 µF bypass capacitor at the false-ground output. The benefit of a large capacitor is that not only does the false-ground present a very low dc resistance to the load, but its ac impedance is low as well. Square Wave Oscillator The oscillator circuit in Figure 7 demonstrates how a rail-to-rail output swing can reduce the effects of power supply variations on the oscillator’s frequency. This feature is especially valuable in battery powered applications, where voltage regulation may not be available. The output frequency remains stable as the supply voltage changes because the RC charging current, which is derived from the rail-to-rail output, is proportional to the supply voltage. Since the Schmitt trigger threshold level is also proportional to supply voltage, the frequency remains relatively independent of supply voltage. For a supply voltage change from 9 V to 5 V, the output frequency only changes about 4 Hz. The slew rate of the amplifier limits the oscillation frequency to a maximum of about 200 Hz at a supply voltage of 5 V. 5V OR 12V 10k⍀ 0.022␮F 240k⍀ 2 7 100⍀ OP196 1␮F 4 3 240k⍀ 2.5V OR 6V 6 1␮F Figure 5. A Micropower False-Ground Generator Single-Supply Half-Wave and Full-Wave Rectifiers An OP296, configured as a voltage follower operating from a single supply, can be used as a simple half-wave rectifier in low frequency (