OPA241

® OPA 241 OPA 425 1 OPA241 OPA2241 OPA4241 OPA 424 1 OPA 225 1 OPA251 OPA2251 OPA4251 Single-Supply, MicroPOWER OPERATIONAL AMPLIFIERS OPA241 Family optimized for +5V supply. OPA251 Family optimized for ±15V supply. DESCRIPTION The OPA241 series and OPA251 series are specifically designed for battery powered, portable applications. In addition to very low power consumption (25µA), these amplifiers feature low offset voltage, rail-to-rail output swing, high common-mode rejection, and high open-loop gain. The OPA241 series is optimized for operation at low power supply voltage while the OPA251 series is optimized for high power supplies. Both can operate from either single (+2.7V to +36V) or dual supplies (±1.35V to ±18V). The input common-mode voltage range extends 200mV below the negative supply—ideal for single-supply applications. They are unity-gain stable and can drive large capacitive loads. Special design considerations assure that these products are easy to use. High performance is maintained as the amplifiers swing to their specified limits. Because the initial offset voltage (±250µV max) is so low, user adjustment is usually not required. However, external trim pins are provided for special applications (single versions only). The OPA241 and OPA251 (single versions) are available in standard 8-pin DIP and SO-8 surface-mount packages. The OPA2241 and OPA2251 (dual versions) come in 8-pin DIP and SO-8 surface-mount packages. The OPA4241 and OPA4251 (quad versions) are available in 14-pin DIP and SO-14 surface-mount packages. All are fully specified from –40°C to +85°C and operate from –55°C to +125°C. FEATURES q q q q MicroPOWER: IQ = 25µA q q q q SINGLE-SUPPLY OPERATION RAIL-TO-RAIL OUTPUT (within 50mV) WIDE SUPPLY RANGE Single Supply: +2.7V to +36V Dual Supply: ±1.35V to ±18V LOW OFFSET VOLTAGE: ±250µV max HIGH COMMON-MODE REJECTION: 124dB HIGH OPEN-LOOP GAIN: 128dB SINGLE, DUAL, AND QUAD APPLICATIONS q BATTERY OPERATED INSTRUMENTS q PORTABLE DEVICES q MEDICAL INSTRUMENTS q TEST EQUIPMENT OPA241, OPA251 Offset Trim –In +In V– 1 2 3 4 8-Pin DIP, SO-8 8 7 6 5 NC V+ Output Offset Trim OPA2241, OPA2251 Out A –In A +In A V– 1 2 3 4 8-Pin DIP, SO-8 A B 8 7 6 5 V+ Out B –In B +In B Out A –In A +In A V+ +In B –In B Out B 1 2 OPA4241, OPA4251 14 13 A 3 4 5 B 6 7 14-Pin DIP, SO-14 C 9 8 –In C Out C D 12 11 10 +In D V– +In C Out D –In D 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 © 1997 Burr-Brown Corporation PDS-1406B 1 OPA241, 2241, 4241 Printed in U.S.A. OPA251, 2251, 4251 October, 1998 ® SPECIFICATIONS: VS = 2.7V to 5V At TA = +25°C, RL = 100kΩ connected to VS/2, unless otherwise noted. Boldface limits apply over the specified temperature range, TA = –40°C to +85°C. OPA241UA, PA OPA2241UA, PA OPA4241UA, PA PARAMETER OFFSET VOLTAGE Input Offset Voltage TA = –40°C to +85°C vs Temperature vs Power Supply TA = –40°C to +85°C Channel Separation (dual, quad) INPUT BIAS CURRENT Input Bias Current(2) TA = –40°C to +85°C Input Offset Current TA = –40°C to +85°C NOISE Input Voltage Noise, f = 0.1Hz to 10Hz Input Voltage Noise Density, f = 1kHz Current Noise Density, f = 1kHz INPUT VOLTAGE RANGE Common-Mode Voltage Range Common-Mode Rejection Ratio TA = –40°C to +85°C INPUT IMPEDANCE Differential Common-Mode OPEN-LOOP GAIN Open-Loop Voltage Gain TA = –40°C to +85°C TA = –40°C to +85°C FREQUENCY RESPONSE Gain-Bandwidth Product Slew Rate Overload Recovery Time OUTPUT Voltage Output Swing from Rail(3) TA = –40°C to +85°C TA = –40°C to +85°C Short-Circuit Current Single Versions Dual, Quad Versions Capacitive Load Drive POWER SUPPLY Specified Voltage Range Operating Voltage Range Quiescent Current (per amplifier) TA = –40°C to +85°C TEMPERATURE RANGE Specified Range Operating Range Storage Range Thermal Resistance 8-Pin DIP SO-8 Surface Mount 14-Pin DIP SO-14 Surface Mount GBW SR AOL RL = 100kΩ, VO = (V–)+100mV to (V+)–100mV RL = 100kΩ, VO = (V–)+100mV to (V+)–100mV RL = 10kΩ, VO = (V–)+200mV to (V+)–200mV RL = 10kΩ, VO = (V–)+200mV to (V+)–200mV 100 100 100 100 VOS dVOS/dT PSRR TA = –40°C to +85°C VS = 2.7V to 36V VS = 2.7V to 36V CONDITION MIN TYP(1) ±50 MAX ±250 OPA251UA, PA OPA2251UA, PA OPA4251UA, PA MIN TYP(1) ±100 MAX UNITS µV µV µV/°C µV/V µV/V µV/V nA nA nA nA µVp-p nV/√Hz fA/√Hz V dB dB Ω || pF Ω || pF dB dB dB dB kHz V/µs µs mV mV mV mV mV mA mA ±100 ±0.4 3 0.3 ±400 30 30 ±130 ±0.6 T T T T IB IOS –4 ±0.1 –20 –25 ±2 ±2 T T en in –0.2 80 80 1 45 40 (V+) –0.8 106 T T T VCM CMRR VCM = –0.2V to (V+) –0.8V VCM = 0V to (V+) –0.8V T 107 || 2 109 || 4 120 120 T T T T VS = 5V, G = 1 VIN • G = VS RL = 100kΩ to VS /2, AOL ≥ 70dB RL = 100kΩ to VS /2, AOL ≥ 100dB RL = 100kΩ to VS /2, AOL ≥ 100dB RL = 10kΩ to VS /2, AOL ≥ 100dB RL = 10kΩ to VS /2, AOL ≥ 100dB 35 0.01 60 50 75 100 T T T T T T VO 100 100 200 200 ISC –24/+4 –30/+4 See Typical Curve +2.7 to +5 +2.7 ±25 +36 ±30 ±36 +85 +125 +125 100 150 80 100 T T T T T T T CLOAD VS IQ TA = –40°C to +85°C IO = 0 IO = 0 V V µA µA °C °C °C °C/W °C/W °C/W °C/W –40 –55 –55 T T T T T T T T T T θJA T Specifications the same as OPA241UA, PA. NOTES: (1) VS = +5V. (2) The negative sign indicates input bias current flows out of the input terminals. (3) Output voltage swings are measured between the output and power supply rails. 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. ® OPA241, 2241, 4241 OPA251, 2251, 4251 2 SPECIFICATIONS: VS = ±15V At TA = +25°C, RL = 100kΩ connected to ground, unless otherwise noted. Boldface limits apply over the specified temperature range, TA = –40°C to +85°C. OPA241UA, PA OPA2241UA, PA OPA4241UA, PA PARAMETER OFFSET VOLTAGE Input Offset Voltage TA = –40°C to +85°C vs Temperature vs Power Supply TA = –40°C to +85°C Channel Separation (dual, quad) INPUT BIAS CURRENT Input Bias Current(1) TA = –40°C to +85°C Input Offset Current TA = –40°C to +85°C NOISE Input Voltage Noise, f = 0.1Hz to 10Hz Input Voltage Noise Density, f = 1kHz Current Noise Density, f = 1kHz INPUT VOLTAGE RANGE Common-Mode Voltage Range Common-Mode Rejection Ratio TA = –40°C to +85°C INPUT IMPEDANCE Differential Common-Mode OPEN-LOOP GAIN Open-Loop Voltage Gain TA = –40°C to +85°C TA = –40°C to +85°C FREQUENCY RESPONSE Gain-Bandwidth Product Slew Rate Overload Recovery Time OUTPUT Voltage Output Swing from Rail(2) TA = –40°C to +85°C TA = –40°C to +85°C Short-Circuit Current Single Versions Dual Versions Capacitive Load Drive POWER SUPPLY Specified Voltage Range Operating Voltage Range Quiescent Current (per amplifier) TA = –40°C to +85°C TEMPERATURE RANGE Specified Range Operating Range Storage Range Thermal Resistance 8-Pin DIP SO-8 Surface Mount 14-Pin DIP SO-14 Surface Mount GBW SR AOL RL = 100kΩ, VO = –14.75V to +14.75V RL = 100kΩ, VO = –14.75V to +14.75V RL = 20kΩ, VO = –14.7V to +14.7V RL = 20kΩ, VO = –14.7V to +14.7V VOS dVOS/dT PSRR TA = –40°C to +85°C VS = ±1.35V to ±18V VS = ±1.35V to ±18V CONDITION MIN TYP ±100 ±150 ±0.6 T T IB IOS T T MAX OPA251UA, PA OPA2251UA, PA OPA4251UA, PA MIN TYP ±50 MAX ±250 UNITS µV µV µV/°C µV/V µV/V µV/V nA nA nA nA µVp-p nV/√Hz fA/√Hz (V+) –0.8 124 V dB dB Ω || pF Ω || pF dB dB dB dB kHz V/µs µs mV mV mV mV mV mA mA ±100 ±0.5 T T 3 0.3 –4 ±0.1 ±300 30 30 –20 –25 ±2 ±2 en in T T T (V–) –0.2 100 100 1 45 40 VCM CMRR VCM = –15.2V to 14.2V VCM = –15V to 14.2V T T T T T 100 100 100 100 107 || 2 109 || 4 128 128 G=1 VIN • G = VS RL = 100kΩ, AOL ≥ 70dB RL = 100kΩ, AOL ≥ 100dB RL = 100kΩ, AOL ≥ 100dB RL = 20kΩ, AOL ≥ 100dB RL = 20kΩ, AOL ≥ 100dB T T T T T T 35 0.01 60 50 75 100 VO 250 250 300 300 ISC T T T T T T T –21/+4 –50/+4 See Typical Curve ±15 ±27 CLOAD VS IQ TA = –40°C to +85°C IO = 0 IO = 0 ±1.35 ±18 ±45 ±38 V V µA µA °C °C °C °C/W °C/W °C/W °C/W T T T T T T T T T T –40 –55 –55 100 150 80 100 +85 +125 +125 θJA T Specifications the same as OPA251UA, PA. NOTES: (1) The negative sign indicates input bias current flows out of the input terminals. (2) Output voltage swings are measured between the output and power supply rails. 3 OPA241, 2241, 4241 OPA251, 2251, 4251 ® ABSOLUTE MAXIMUM RATINGS(1) Supply Voltage, V+ to V– .................................................................... 36V Input Voltage(2) .................................................. (V–) –0.5V to (V+) +0.5V Output Short Circuit to Ground(3) ............................................ Continuous Operating Temperature .................................................. –55°C to +125°C Storage Temperature ..................................................... –55°C to +125°C Junction Temperature ...................................................................... 150°C Lead Temperature (soldering, 10s) ................................................. 300°C NOTES: (1) Stresses above these ratings may cause permanent damage. (2) Input terminals are diode-clamped to the power supply rails. Input signals that can swing more that 0.5V beyond the supply rails should be currentlimited to 5mA or less. (3) One amplifier per package. ELECTROSTATIC DISCHARGE SENSITIVITY This integrated circuit can be damaged by ESD. Burr-Brown 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 SPECIFIED VOLTAGE OPERATING VOLTAGE RANGE PACKAGE DRAWING NUMBER(1) SPECIFICATION TEMPERATURE RANGE PRODUCT OPA241 SERIES Single OPA241PA OPA241UA Dual OPA2241PA OPA2241UA Quad OPA4241PA OPA4241UA OPA251 SERIES Single OPA251PA OPA251UA Dual OPA2251PA OPA2251UA Quad OPA4251PA OPA4251UA PACKAGE 2.7V to 5V 2.7V to 5V 2.7V to 5V 2.7V to 5V 2.7V to 5V 2.7V to 5V 2.7V to 36V 2.7V to 36V 2.7V to 36V 2.7V to 36V 2.7V to 36V 2.7V to 36V 8-Pin DIP SO-8 Surface Mount 8-Pin DIP SO-8 Surface Mount 14-Pin DIP SO-14 Surface Mount 006 182 006 182 010 235 –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C ±15V ±15V ±15V ±15V ±15V ±15V 2.7V to 36V 2.7V to 36V 2.7V to 36V 2.7V to 36V 2.7V to 36V 2.7V to 36V 8-Pin DIP SO-8 Surface Mount 8-Pin DIP SO-8 Surface Mount 14-Pin DIP SO-14 Surface Mount 006 182 006 182 010 235 –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C –40°C to +85°C NOTE: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. ® OPA241, 2241, 4241 OPA251, 2251, 4251 4 TYPICAL PERFORMANCE CURVES At TA = +25°C, and RL = 100kΩ connected to VS/2 (ground for VS = ±15V), unless otherwise noted. Curves apply to OPA241 and OPA251 unless specified. OPEN-LOOP GAIN/PHASE vs FREQUENCY 160 140 120 180 160 140 G Φ 120 140 POWER SUPPLY and COMMON-MODE REJECTION RATIO vs FREQUENCY VS = ±15V VS = ±5V CMRR 100 80 60 40 20 0 0.1 1 10 100 Frequency (Hz) 1k 10k 100k –PSRR +PSRR Power Supply Rejection Ratio (dB) 120 Voltage Gain (dB) 100 80 60 40 20 0 –20 0.01 100 80 60 VS = ±15V VS = +5V 40 20 10 100 1k 10k 0 100k 0.1 1 Frequency (Hz) Phase (°) CHANNEL SEPARATION vs FREQUENCY 140 130 INPUT VOLTAGE AND CURRENT NOISE SPECTRAL DENSITY vs FREQUENCY 1k 1k Channel Separation (dB) Voltage Noise (nV/÷Hz) 120 110 100 90 80 70 10 100 1k Frequency (Hz) 10k 100k Dual and quad devices. G = 1, all channels. Quad measured channel A to D or B to C—other combinations yield improved rejection. 100 Current Noise 100 Voltage Noise 10 0.1 1 10 100 1k 10k Frequency (Hz) 10 QUIESCENT CURRENT vs SUPPLY VOLTAGE 30 Per Amplifier QUIESCENT CURRENT vs TEMPERATURE 40 Per Amplifier Quiescent Current (µA) Quiescent Current (µA) 28 35 VS = ±15V 30 26 25 VS = +5V 24 20 22 0 5 10 15 20 25 30 35 40 Total Supply Voltage (V) 15 –75 –50 –25 0 25 50 75 100 125 Temperature (°C) 5 OPA241, 2241, 4241 OPA251, 2251, 4251 ® Current Noise (fA/√Hz) TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°C, and RL = 100kΩ connected to VS/2 (ground for VS = ±15V), unless otherwise noted. Curves apply to OPA241 and OPA251 unless specified. INPUT BIAS CURRENT vs TEMPERATURE –6 –5 IB INPUT BIAS CURRENT vs INPUT COMMON-MODE VOLTAGE Input Bias Current (nA) –4 IB –2 IOS 0 Input Bias Current (nA) –4 –3 –2 –1 IOS 0 2 –75 –50 –25 0 25 50 75 100 125 Temperature (°C) 0 5 10 15 20 25 30 Common-Mode Voltage (V) SHORT-CIRCUIT CURRENT vs TEMPERATURE 50 45 Short-Circuit Current (mA) COMMON-MODE REJECTION vs TEMPERATURE 140 VS = ±15V VS = +2.7V, +5V VS = ±15V –ISC VS = +5V 40 35 30 25 20 15 10 5 0 –75 Common-Mode Rejection (dB) 120 100 80 60 40 20 0 VS = +5V Single Versions Dual, Quad Versions VS = ±15V +ISC, VS = +5V, ±15V (all versions) VCM = (V–) –0.2V to (V+) –0.8V VCM = (V–) –0.1V to (V+) –0.8V VCM = (V–) to (V+) –0.8V –75 –50 –25 0 25 50 75 100 125 –50 –25 0 25 50 75 100 125 Temperature (°C) Temperature (°C) OPEN-LOOP GAIN AND POWER SUPPLY REJECTION vs TEMPERATURE 140 OUTPUT VOLTAGE SWING vs OUTPUT CURRENT (V+) T = +25°C (V+) –0.1V Output Voltage Swing (V) 130 RL = 20kΩ, 100kΩ T = –55°C (V+) –0.2V (V+) –0.3V (V–) +0.3V T = +125°C (V–) +0.2V (V–) +0.1V (V–) T = +25°C, –55°C T = +125°C AOL, PSR (dB) RL = 100kΩ 120 RL = 10kΩ 110 AOL, VS = ±15V AOL, VS = +5V 100 –75 –50 –25 0 25 50 75 100 125 Temperature (°C) PSRR 0.1 ±1 Output Current (mA) ±10 ® OPA241, 2241, 4241 OPA251, 2251, 4251 6 TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°C, and RL = 100kΩ connected to VS/2 (ground for VS = ±15V), unless otherwise noted. Curves apply to OPA241 and OPA251 unless specified. OPEN-LOOP GAIN vs OUTPUT VOLTAGE SWING 140 130 Open-Loop Gain (dB) MAXIMUM OUTPUT VOLTAGE vs FREQUENCY 30 Maximum output voltage without slew rate-induced distortion. RL = 100kΩ Maximum Output Voltage (Vp-p) VS = ±15V VS = +5V VS = +2.7V RL = 20kΩ 25 20 15 10 5 0 VS = +5V VS = 2.7V 10 VS = ±15V 120 110 100 90 80 500 RL = 10kΩ 400 300 200 100 0 100 1k Frequency (Hz) 10k 100k Output Voltage Swing from Rail (mV) OPA241 SERIES OFFSET VOLTAGE PRODUCTION DISTRIBUTION 30 25 Typical production distribution of packaged units. Singles, duals, and quads included. VS = +5V OPA241 SERIES OFFSET VOLTAGE DRIFT PRODUCTION DISTRIBUTION 20 18 VS = +5V Typical production distribution of packaged units. Singles, duals, and quads included. Percent of Amplifiers (%) Percent of Amplifiers (%) 16 14 12 10 8 6 4 2 20 15 10 5 0 0 –225 –200 –175 –150 –125 –100 –75 –50 –25 0 25 50 75 100 125 150 175 200 225 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 Offset Voltage (µV/°C) Offset Voltage (µV) OPA251 SERIES OFFSET VOLTAGE PRODUCTION DISTRIBUTION 30 VS = ±15V 25 Typical production distribution of packaged units. Singles, duals, and quads included. 18 16 OPA251 SERIES OFFSET VOLTAGE DRIFT PRODUCTION DISTRIBUTION VS = ±15V Typical production distribution of packaged units. Singles, duals, and quads included. Percent of Amplifiers (%) Percent of Amplifiers (%) 14 12 10 8 6 4 2 20 15 10 5 0 0 –225 –200 –175 –150 –125 –100 –75 –50 –25 0 25 50 75 100 125 150 175 200 225 Offset Voltage (µV) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 Offset Voltage Drift (µV/°C) 7 OPA241, 2241, 4241 OPA251, 2251, 4251 ® TYPICAL PERFORMANCE CURVES (CONT) At TA = +25°C, and RL = 100kΩ connected to VS/2 (ground for VS ±15V), unless otherwise noted. Curves apply to OPA241 and OPA251 unless specified. QUIESCENT CURRENT PRODUCT DISTRIBUTION 25 VS = +5V Typical production distribution of packaged units. Singles, duals, and quads included. QUIESCENT CURRENT PRODUCTION DISTRIBUTION 35 VS = ±15V 30 Percent of Amplifiers (%) Percent of Amplifiers (%) 20 Per Amplifier 15 Typical production distribution of packaged units. Singles, duals, and quads included. 25 20 15 10 Per Amplifier 5 10 5 0 0 21 21.5 22 22.5 23 23.5 24 24.5 25 25.5 26 26.5 27 27.5 28 28.5 29 29.5 30 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 Quiescent Current (µA) Quiescent Current (µA) OPA241 SMALL-SIGNAL STEP RESPONSE VS = +5V, G = +1, RL = 100kΩ, CL = 100pF OPA241 LARGE-SIGNAL STEP RESPONSE VS = +5V, G + 1, RL = 100kΩ, CL = 100pF 50mV/div 0.5V/div 200µs/div 200µs/div OPA251 SMALL-SIGNAL STEP RESPONSE VS = ±15V, G = +1, RL = 100kΩ, CL = 500pF OPA251 LARGE-SIGNAL STEP RESPONSE VS = ±15V, G = +1, RL = 100kΩ, CL = 500pF 50mV/div 200µs/div 2V/div 2ms/div ® OPA241, 2241, 4241 OPA251, 2251, 4251 8 38 APPLICATIONS INFORMATION The OPA241 and OPA251 series are unity-gain stable and suitable for a wide range of general purpose applications. Power supply pins should be bypassed with 0.01µF ceramic capacitors. OPERATING VOLTAGE The OPA241 series is laser-trimmed for low offset voltage and drift at low supply voltage (VS = +5V). The OPA251 series is trimmed for ±15V operation. Both products operate over the full voltage range (+2.7V to +36V or ±1.35V to ±18V) with some compromises in offset voltage and drift performance. However, all other parameters have similar performance. Key parameters are guaranteed over the specified temperature range, –40°C to +85°C. Most behavior remains unchanged throughout the full operating voltage range. Parameters which vary significantly with operating voltage or temperature are shown in typical performance curves. OFFSET VOLTAGE TRIM As mentioned previously, offset voltage of the OPA241 series is laser-trimmed at +5V. The OPA251 series is trimmed at ±15V. Because the initial offset is so low, user adjustment is usually not required. However, the OPA241 and OPA251 (single op amp versions) provide offset voltage trim connections on pins 1 and 5. Offset voltage can be adjusted by connecting a potentiometer as shown in Figure 1. This adjustment should be used only to null the offset of the op amp, not to adjust system offset or offset produced by the signal source. Nulling offset could degrade the offset drift behavior of the op amp. While it is not possible to predict the exact change in drift, the effect is usually small. Figures 2 and 3 show the regions where the OPA241 series and OPA251 series have the potential for instability. As shown, the unity gain configuration with low supplies is the most susceptible to the effects of capacitive load. With VS = +5V, G = +1, and IOUT = 0, operation remains stable with load capacitance up to approximately 200pF. Increasing supply voltage, output current, and/or gain significantly improves capacitive load drive. For example, increasing the supplies to ±15V and gain to 10 allows approximately 2700pF to be driven. One method of improving capacitive load drive in the unity gain configuration is to insert a resistor inside the feedback loop as shown in Figure 4. This reduces ringing with large capacitive loads while maintaining dc accuracy. For example, with VS = ±1.35V and RS = 5kΩ, the OPA241 series and OPA251 series perform well with capacitive loads in excess of 1000pF. Without the series resistor, capacitive load drive is typically 200pF for these conditions. However, this method will result in a slight reduction of output voltage swing. 100k VS = +2.7V VS = +5V Capacitive Load (pF) Operation above selected gain curve not recommended 10k G = 10 1k Sinking G = –1 Sourcing G = +1 100 –1 –0.1 –0.01 0 0.01 0.1 1 Output Current (mA) V+ 0.01µF 7 2 3 OPA241 OPA241 and OPA251 (single op amps) only. FIGURE 2. Stability—Capacitive Load versus Output Current for Low Supply Voltage. Use offset adjust pins only to null offset voltage of op amp—see text. 6 5 1 100kΩ 100k VS = ±15V Operation above selected gain curve not recommended 0.01µF 4 Capacitive Load (pF) Trim Range: ±2mV (V–) = 0V for single-supply operation. V– 10k G = 10 G = –1 1k Sinking 100 G = +1 Sourcing FIGURE 1. OPA241 and OPA251 Offset Voltage Trim Circuit. CAPACITIVE LOAD AND STABILITY The OPA241 series and OPA251 series can drive a wide range of capacitive loads. However, all op amps under certain conditions may be unstable. Op amp configuration, gain, and load value are just a few of the factors to consider when determining stability. 9 –1 –0.1 –0.01 0 0.01 0.1 1 Output Current (mA) FIGURE 3. Stability—Capacitive Load versus Output Current for ±15V Supplies. OPA241, 2241, 4241 OPA251, 2251, 4251 ® RS 5kΩ OPA241 VIN CL VOUT FIGURE 4. Series Resistor in Unity Gain Configuration Improves Capacitive Load Drive. RH 10Ω To Load IH R1 38.3kΩ R3 38.3kΩ R5 383kΩ V+ –In A1 +In OPA241 Out VO = 10 • IH • RH High-Side Current Sense V+ for A1, A2 + 2.7V to ±15V R8 100kΩ V+ –In A2 +In OPA241 Out R4 20kΩ R2 19.1kΩ V– R2 and R4 divide down the common-mode input to A1. V– for A1, A2 VO = 10 • IL • RL R6 10kΩ RL 10Ω IL V– R7 9.09kΩ Low-Side Current Sense Common-mode range of A2 extends to V– for low-side sensing. Optional for IB Cancellation (R7 = R6 II R8) To Load NOTE: Low and high-side sensing circuits can be used independently. FIGURE 5. Low and High-Side Battery Current Sensing. ® OPA241, 2241, 4241 OPA251, 2251, 4251 10