LT1677I

Final Electrical Specifications LT1677 Low Noise, Rail-to-Rail Precision Op Amp February 2000 FEATURES s s DESCRIPTIO s s s s s s s s s s Rail-to-Rail Input and Output 100% Tested Low Voltage Noise: 3.2nV/√Hz Typ at 1kHz 4.5nV/√Hz Max at 1kHz Offset Voltage: 60µV Max Low VOS Drift: 0.2µV/°C Typ Low Input Bias Current: 20nA Max Wide Supply Range: 3V to ±15V High AVOL: 4V/µV Min, RL = 1k High CMRR: 109dB Min High PSRR: 108dB Min Gain Bandwidth Product: 7.2MHz Slew Rate: 2.5V/µs Operating Temperature Range: – 40°C to 85°C APPLICATIO S s s s s s s The LT ®1677 features the lowest noise performance available for a rail-to-rail operational amplifier: 3.2nV/√Hz wideband noise, 1/f corner frequency of 13Hz and 70nV peak-to-peak 0.1Hz to 10Hz noise. Low noise is combined with outstanding precision: 20µV offset voltage and 0.2µV/°C drift, 130dB common mode and power supply rejection and 7.2MHz gain bandwidth product. The common mode range exceeds the power supply by 100mV. The voltage gain of the LT1677 is extremely high, especially with a single supply: 20 million driving a 1k load. In the design, processing and testing of the device, particular attention has been paid to the optimization of the entire distribution of several key parameters. Consequently, the specifications of even the lowest cost grade have been spectacularly improved compared to competing rail-to-rail amplifiers. , LTC and LT are registered trademarks of Linear Technology Corporation. Low Noise Signal Processing Microvolt Accuracy Threshold Detection Strain Gauge Amplifiers Tape Head Preamplifiers Direct Coupled Audio Gain Stages Infrared Detectors TYPICAL APPLICATIO Precision High Side Current Sense SOURCE RIN 1k LOAD Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. + 3 – RLINE 0.1Ω 2 7 LT1677 4 6 ZETEX BC856B VOUT ROUT VOUT ROUT 20k ILOAD = RLINE RIN = 2V/AMP 1677 TA01 U U U 1 LT1677 ABSOLUTE AXI U RATI GS (Note 1) Operating Temperature Range LT1677C (Note 4) ............................. – 40°C to 85°C LT1677I ............................................. – 40°C to 85°C Specified Temperature Range LT1677C (Note 5) ............................. – 40°C to 85°C LT1677I ............................................. – 40°C to 85°C Supply Voltage ...................................................... ± 22V Input Voltages (Note 2) ............ 0.3V Beyond Either Rail Differential Input Current (Note 2) ..................... ± 25mA Output Short-Circuit Duration (Note 3) ............ Indefinite Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec.)................. 300°C PACKAGE/ORDER I FOR ATIO TOP VIEW VOS TRIM 1 –IN 2 +IN 3 V– 4 N8 PACKAGE 8-LEAD PDIP TJMAX = 150°C, θJA = 130°C/ W VOS 8 TRIM ORDER PART NUMBER LT1677CN8 LT1677IN8 – + 7 6 5 V+ OUT NC Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS SYMBOL VOS PARAMETER Input Offset Voltage TA = 25°C, VS = ±15V, VCM = VO = 0V unless otherwise noted. MIN TYP 20 150 1.5 0.3 ±2 0.16 – 0.4 3 5 20 70 33 100 5.2 25 7 3.2 17 5.3 4.5 ± 20 0.4 15 25 200 MAX 60 400 5 UNITS µV µV mV µV/Mo nA µA µA nA nA nA nVP-P nVP-P nVP-P nV/√Hz nV/√Hz nV/√Hz nV/√Hz nV/√Hz nV/√Hz CONDITIONS (Note 6) VCM = 14V to 15.1V VCM = – 13.3V to –15.1V ∆VOS ∆Time IB Long Term Input Voltage Stability Input Bias Current VCM = 14V to 15.1V VCM = – 13.3V to –15.1V – 1.5 IOS Input Offset Current VCM = 14V to 15.1V VCM = – 13.3V to –15.1V en Input Noise Voltage 0.1Hz to 10Hz (Note 7) VCM = 15V VCM = –15V VCM = 0V, fO = 10Hz VCM = 15V, fO = 10Hz VCM = – 15V, fO = 10Hz VCM = 0V, fO = 1kHz (Note 8) VCM = 15V, fO = 1kHz VCM = – 15V, fO = 1kHz Input Noise Voltage Density 2 U U W WW U W TOP VIEW VOS 1 TRIM –IN 2 +IN 3 V– 4 8 VOS TRIM V+ OUT NC ORDER PART NUMBER LT1677CS8 LT1677IS8 S8 PART MARKING 1677 1677I – + 7 6 5 S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 150°C, θJA = 190°C/ W LT1677 ELECTRICAL CHARACTERISTICS SYMBOL in VCM RIN CIN CMRR PSRR AVOL PARAMETER Input Noise Current Density Input Voltage Range Input Resistance Input Capacitance Common Mode Rejection Ratio Power Supply Rejection Ratio Large-Signal Voltage Gain Common Mode VS = ±2.5V VCM = – 13.3V to 14.0V VCM = ±15.1V VS = ±1.7V to ±18V VS = 2.7V to 40V, VCM = VO = 1.7V RL ≥ 10k, VO = ±14V RL ≥ 1k, VO = ±13.5V RL ≥ 600Ω, VO = ±10V VCC = 5V or 3V, VEE = 0V, VCM = 1.7V, RL to GND, VOUT = 0.5V to: RL ≥ 10k, VCC – 0.5V RL ≥ 1k, VCC – 0.7V VOL Output Voltage Swing Low Above VEE ISINK = 0.1mA ISINK = 2.5mA ISINK = 10mA Below VCC ISOURCE = 0.1mA ISOURCE = 2.5mA ISOURCE = 10mA 25 RL ≥ 10k (Note 9) fO = 100kHz RL = 2k, AV = 1, fO = 1kHz, VO = 10VP-P 10V Step 0.1%, AV = +1 10V Step 0.01%, AV = +1 IOUT = 0 AV = 100, f = 10kHz 1.7 4.5 109 74 106 108 7 4 0.4 TA = 25°C, VS = ±15V, VCM = VO = 0V unless otherwise noted. MIN TYP 1.2 0.3 ±15.1 ±15.2 2 3.8 4.2 130 95 130 125 25 20 0.7 MAX UNITS pA/√Hz pA/√Hz V GΩ pF pF dB dB dB dB V/µV V/µV V/µV CONDITIONS (Note 6) fO = 10Hz fO = 1kHz 2 1.5 10 4 80 110 300 110 190 500 35 2.5 7.2 0.0006 5 6 80 1 2.75 3.5 170 250 500 170 300 700 V/µV V/µV mV mV mV mV mV mV mA V/µs MHz % µs µs Ω Ω mA VOH Output Voltage Swing High ISC SR GBW THD tS RO IS Output Short-Circuit Current (Note 3) Slew Rate Gain Bandwidth Product Total Harmonic Distortion Settling Time Open-Loop Output Resistance Closed-Loop Output Resistance Supply Current 3 LT1677 The q denotes the specifications which apply over the temperature range of 0°C < TA < 70°C. VS = ±15V, VCM = VO = 0V unless otherwise noted. SYMBOL VOS PARAMETER Input Offset Voltage VCM = 14.0V to 14.8V VCM = – 13.3V to –15V ∆VOS ∆Temp IB Average Input Offset Drift Input Bias Current VCM = 14.0V to 14.8V VCM = – 13.3V to –15V IOS Input Offset Current VCM = 14.0V to 14.8V VCM = – 13.3V to –15V VCM CMRR PSRR AVOL Input Voltage Range Common Mode Rejection Ratio Power Supply Rejection Ratio Large-Signal Voltage Gain VCM = – 13.3V to 14.0V VCM = – 15V to 14.8V VS = ±1.7V to ±18V VS = 2.8V to 40V, VCM = VO = 1.7V RL ≥ 10k, VO = ±14V RL ≥ 1k, VO = ±13.5V RL ≥ 600Ω, VO = ±10V VCC = 5V or 3V, VEE = 0V, VCM = 1.7V, VOUT = 0.4V to: RL ≥ 10k, VCC – 0.5V RL ≥ 1k, VCC – 0.7V VOL Output Voltage Swing Low Above VEE ISINK = 0.1mA ISINK = 2.5mA ISINK = 10mA Below VCC ISOURCE = 0.1mA ISOURCE = 2.5mA ISOURCE = 10mA RL ≥ 10k (Note 9) fO = 100kHz SO-8 N8 (Note 10) CONDITIONS (Note 6) q q q q q q q q q q q q q q q q q q q ELECTRICAL CHARACTERISTICS MIN TYP 30 180 1.8 0.40 0.20 ±3 0.19 – 0.43 2 90 90 MAX 120 550 6 2 0.5 ± 35 0.6 20 220 350 14.8 UNITS µV µV mV µV/°C µV/°C nA µA µA nA nA nA V dB dB dB dB V/µV V/µV V/µV –2 –15 106 73 104 106 4 2 0.3 126 93 127 122 20 10 0.5 q q q q q q q q q q q q 3 0.5 8 4 85 160 400 140 230 580 200 320 600 200 350 800 V/µV V/µV mV mV mV mV mV mV mA V/µs MHz 3.9 mA VOH Output Voltage Swing High ISC SR GBW IS Output Short-Circiut Current (Note 3) Slew Rate Gain Bandwidth Product Supply Current 20 1.5 27 2.3 6.2 3.0 4 LT1677 The q denotes the specifications which apply over the temperature range of – 40°C < TA < 85°C. VS = ±15V, VCM = VO = 0V unless otherwise noted. (Note 5) SYMBOL VOS PARAMETER Input Offset Voltage VCM = 14.0V to 14.7V VCM = – 13.3V to –15V ∆VOS ∆Temp IB Average Input Offset Drift Input Bias Current VCM = 14.0V to 14.7V VCM = – 13.3V to –15V IOS Input Offset Current VCM = 14.0V to 14.7V VCM = – 13.3V to –15V VCM CMRR PSRR AVOL Input Voltage Range Common Mode Rejection Ratio Power Supply Rejection Ratio Large-Signal Voltage Gain VCM = –13.3V to 14.0V VCM = –15V to 14.7V VS = ±1.7V to ±18V VS = 3.1V to 40V, VCM = VO = 1.7V RL ≥ 10k, VO = ±14V RL ≥ 1k, VO = ±13.5V RL ≥ 600Ω, VO = ±10V VCC = 5V or 3V, VEE = 0V, VCM = 1.7V, VOUT = 0.5V to: RL ≥ 10k, VCC – 0.5V RL ≥ 1k, VCC – 0.7V VOL Output Voltage Swing Low Above VEE ISINK = 0.1mA ISINK = 2.5mA ISINK = 10mA Below VCC ISOURCE = 0.1mA ISOURCE = 2.5mA ISOURCE = 10mA RL ≥ 10k (Note 9) fO = 100kHz SO-8 N8 (Note 10) CONDITIONS (Note 6) q q q q q q q q q q q q q q q q q q q ELECTRICAL CHARACTERISTICS MIN TYP 45 200 2 0.40 0.20 ±7 0.25 – 0.45 6 100 100 MAX 180 650 6.5 2.0 0.5 ± 50 0.75 40 250 400 14.7 UNITS µV µV mV µV/°C µV/°C nA µA µA nA nA nA V dB dB dB dB V/µV V/µV V/µV – 2.3 –15 105 72 103 105 3 1.5 0.2 124 91 125 120 17 8 0.35 q q q q q q q q q q q q 2 0.2 15 2 90 175 450 150 250 600 230 350 650 250 375 850 V/µV V/µV mV mV mV mV mV mV mA V/µs MHz 4.0 mA VOH Output Voltage Swing High ISC SR GBW IS Output Short-Circuit Current (Note 3) Slew Rate Gain Bandwidth Product Supply Current 18 1.2 25 2.0 5.8 3.1 Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note 2: The inputs are protected by back-to-back diodes. Current limiting resistors are not used in order to achieve low noise. If differential input voltage exceeds ±1.4V, the input current should be limited to 25mA. If the common mode range exceeds either rail, the input current should be limited to 10mA. Note 3: A heat sink may be required to keep the junction temperature below absolute maximum. Note 4: The LT1677C and LTC1677I are guaranteed functional over the Operating Temperature Range of – 40°C to 85°C. Note 5: The LT1677C is guaranteed to meet specified performance from 0°C to 70°C. The LT1677C is designed, characterized and expected to meet specified performance from –40°C to 85°C but is not tested or QA sampled at these temperatures. The LT1677I is guaranteed to meet the extended temperature limits. Note 6: Typical parameters are defined as the 60% yield of parameter distributions of individual amplifier; i.e., out of 100 LT1677s, typically 60 op amps will be better than the indicated specification. Note 7: See the test circuit and frequency response curve for 0.1Hz to 10Hz tester in the Applications Information section of the LT1677 data sheet. Note 8: Noise is 100% tested. Note 9: Slew rate is measured in AV = – 1; input signal is ± 7.5V, output measured at ±2.5V. Note 10: This parameter is not 100% tested. 5 LT1677 TYPICAL PERFOR A CE CHARACTERISTICS Voltage Noise vs Frequency 100 RMS CURRENT NOISE DENSITY (pA/√Hz) RMS VOLTAGE NOISE DENSITY (nV/√Hz) 1/f CORNER 10Hz VCM > 14.5V 1/f CORNER 8.5Hz 10 VCM –13.5V TO 14.5V 1/f CORNER 13Hz VS = ± 15V TA = 25°C 1 10 100 FREQUENCY (Hz) 1000 1677 G03 RMS VOLTAGE NOISE DENSITY (nV/√Hz) VCM < – 14.5V 1 0.1 Input Bias Current Over the Common Mode Range 800 VS = ± 15V 600 TA = 25°C INPUT BIAS CURRENT (nA) OFFSET VOLTAGE (mV) 200 0 VCM = – 13.6V VCM = 15.15V 1.0 0.5 0 –0.5 –1.0 –1.5 –2.0 100 50 0 –50 –100 VOLTAGE OFFSET (µV) 400 INPUT BIAS CURRENT VCM = 14.3V –200 VCM = – 15.3V –400 –600 –800 0 4 –16 –12 –8 –4 8 12 COMMON MODE INPUT VOLTAGE (V) 16 Common Mode Range vs Temperature 2.5 2.0 1.5 VS = ± 2.5V TO ± 15V 250 200 PERCENT OF UNITS (%) OFFSET VOLTAGE CHANGE (µV) OFFSET VOLTAGE (mV) 1.0 0.5 0 –0.5 –1.0 –1.5 –2.0 125°C 25°C –55°C –55°C VOS IS REFERRED 125°C TO VCM = 0V –2.5 –1.0 VEE 1.0 2.0 –0.8 –0.4 VCC VCM – VCC (V) VCM – VEE (V) 6 UW 1677 G06 Current Noise vs Frequency 10 VS = ± 15V TA = 25°C 7 Voltage Noise vs Temperature VS = ±15V VCM = 0V 10Hz 5 6 VCM < –13.5V 1/f CORNER 180Hz 1 VCM –13.5V TO 14.5V 4 1kHz 3 1/f CORNER 90Hz 1/f CORNER 60Hz 0.1 10 VCM > 14.5V 10000 1677 G04 100 1000 FREQUENCY (Hz) 2 –50 –25 50 25 0 75 TEMPERATURE (°C) 100 125 1677 G05 Offset Voltage Shift vs Common Mode 2.5 2.0 1.5 VOS IS REFERRED TO VCM = 0V 250 200 150 VOS vs Temperature of Representative Units 140 120 100 80 60 40 20 0 –20 –40 –60 –80 –55 –35 –15 5 25 45 65 85 105 125 TEMPERATURE (°C) 1677 G11 VS = ± 15V VCM = 0V SO-8 N8 OFFSET VOLTAGE (µV) –2.5 –1.0 VEE 1.0 –150 VS = ± 1.5V TO ± 15V TA = 25°C –200 5 TYPICAL PARTS –250 2.0 –0.8 –0.4 VCC 0.4 VCM – VCC (V) 1677 G08 VCM – VEE (V) Distribution of Input Offset Voltage Drift (N8) 20 18 16 VS = ± 15V TA = – 40°C TO 85°C 120 PARTS (2 LOTS) 5 4 3 2 1 0 –1 –2 –3 –4 –5 Long-Term Stability of Four Representative Units 150 OFFSET VOLTAGE (µV) 100 50 0 –50 14 12 10 8 6 4 2 0 –0.25 –0.15 –0.05 0.05 0.15 0.25 0.35 0.45 INPUT OFFSET VOLTAGE DRIFT (µV/°C) 1677 G02 25°C –100 –150 –200 0.4 –250 0 100 200 300 400 500 600 700 800 900 TIME (HOURS) 1677 G13 1677 G09 LT1677 TYPICAL PERFOR A CE CHARACTERISTICS Supply Current vs Supply Voltage 4 COMMON MODE REJECTION RATIO (dB) 160 POWER SUPPLY REJECTION RATIO (dB) SUPPLY CURRENT (mA) TA = 125°C 3 TA = 25°C TA = – 55°C 2 1 0 ±5 ± 10 ± 15 SUPPLY VOLTAGE (V) Voltage Gain vs Frequency 180 VS = ± 15V TA = 25°C VOLTAGE GAIN (dB) 140 VOLTAGE GAIN (dB) 100 VCM = 0V VCM = VCC 30 20 10 0 –10 60 40 20 0 –20 100 1677 G17 OVERSHOOT (%) 60 VCM = VEE 20 –20 0.01 1 10k 100 FREQUENCY (Hz) PM, GBWP, SR vs Temperature PHASE MARGIN (DEG) GAIN BANDWIDTH PRODUCT, fO = 100kHz (MHz) 70 PHASE 60 GBW 50 SLEW RATE (V/µs) 3 SLEW 2 1 –50 –25 50 25 0 75 TEMPERATURE (°C) UW 1677 G28 Common Mode Rejection Ratio vs Frequency VS = ± 15V 140 TA = 25°C VEM = 0V 120 100 80 60 40 20 0 1k 10k 100k 1M FREQUENCY (Hz) 10M 1677 G14 Power Supply Rejection Ratio vs Frequency 160 140 120 100 NEGATIVE SUPPLY 80 POSITIVE SUPPLY 60 40 20 0 1 10 100 10k 1k FREQUENCY (Hz) 100k 1M VS = ± 15V TA = 25°C ± 20 1677 G15 Gain, Phase Shift vs Frequency 50 40 VS = ± 15V VCM = 0V TA = 25°C 80 CL = 10pF 100 60 50 Overshoot vs Load Capacitance VS = ±15V TA = 25°C RL = 10k TO 2k PHASE SHIFT (DEG) 40 30 20 10 0 10 100 CAPACITANCE (pF) 1000 1677 G30 RISING EDGE FALLING EDGE 1M 100M 1677 G16 0.1 1 10 FREQUENCY (MHz) Large-Signal Transient Response Small-Signal Transient Response VS = ± 15V CL = 15pF 10V 50mV 8 7 6 5 4 0 – 10V – 50mV AVCL = – 1 VS = ± 15V AVCL = 1 VS = ± 15V CL = 15pF 100 125 1677 G29 7 LT1677 TYPICAL PERFOR A CE CHARACTERISTICS Settling Time vs Output Step (Inverting) 12 10 SETTLING TIME (µs) VIN VIN RL = 1k 8 6 4 2 VS = ± 15V AV = – 1 TA = 25°C 0.1% OF FULL SCALE 0.01% OF FULL SCALE 8 6 4 0.1% OF 2 FULL SCALE 0 –10 –8 –6 –4 –2 0 2 4 OUTPUT STEP (V) 0.1% OF FULL SCALE 0.01% OF FULL SCALE 0.01% OF FULL SCALE OUTPUT VOLTAGE SWING (V) SETTLING TIME (µs) 0.1% OF FULL SCALE 0 –10 –8 –6 –4 –2 0 2 4 OUTPUT STEP (V) 6 8 10 1677 G32 Output Short-Circuit Current vs Time 50 SHORT-CIRCUIT CURRENT (mA) SINKING SOURCING 40 30 20 10 VS = ± 15V 100 –55°C Closed-Loop Output Impedance vs Frequency TOTAL HARMONIC DISTROTION + NOISE (%) OUTPUT IMPEDANCE (Ω) 25°C 125°C 10 1 AV = +100 0.1 AV = +1 0.01 –30 –35 –40 –45 –50 0 125°C –55°C 25°C 0.001 3 2 4 1 TIME FROM OUTPUT SHORT TO GND (MIN) 1677 G23 10 100 10k 1k FREQUENCY (Hz) Total Harmonic Distortion and Noise vs Frequency for Inverting Gain TOTAL HARMONIC DISTORTION + NOISE (%) TOTAL HARMONIC DISTROTION + NOISE (%) 0.1 ZL = 2k/15pF VO = 20VP-P AV = –1, –10, – 100 MEASUREMENT BANDWIDTH = 10Hz TO 80kHz 1 Total Harmonic Distortion and Noise vs Output Amplitude for Noninverting Gain ZL = 2k/15pF fO = 1kHz AV = +1, +10, +100 MEASUREMENT BANDWIDTH = 10Hz TO 22kHz AV = 100 0.01 AV = 10 0.001 AV = 1 TOTAL HARMONIC DISTORTION + NOISE (%) 0.1 0.01 AV = – 100 0.001 AV = – 10 AV = – 1 0.0001 20 100 1k FREQUENCY (Hz) 10k 20k 1677 G25 0.0001 0.3 1 10 OUTPUT SWING (VP-P) 30 1677 G26 8 + VOUT 10 2k – + – 0.01% OF FULL SCALE 5k UW 5k Settling Time vs Output Step (Noninverting) 12 VS = ± 15V AV = 1 TA = 25°C 2k VOUT Output Voltage Swing vs Load Current V+ 0 VS = ± 15V 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.5 125°C 0.4 25°C 0.3 0.2 –55°C 0.1 V– 0 –10 –8 –6 –4 –2 0 2 4 6 8 ISOURCE ISINK OUTPUT CURRENT (mA) 10 –55°C 25°C 125°C 6 8 10 1677 G33 1677 G22 Total Harmonic Distortion and Noise vs Frequency for Noninverting Gain 0.1 ZL = 2k/15pF VO = 20VP-P AV = +1, +10, +100 MEASUREMENT BANDWIDTH = 10Hz TO 80kHz AV = 100 0.01 0.001 AV = 10 AV = 1 0.0001 20 100 1k FREQUENCY (Hz) 10k 20k 1677 G24 100k 1M 1677 G31 Total Harmonic Distortion and Noise vs Output Amplitude for Inverting Gain 1 ZL = 2k/15pF fO = 1kHz AV = –1, –10, –100 MEASUREMENT BANDWIDTH = 10Hz TO 22kHz AV = –100 AV = – 10 0.001 AV = – 1 0.1 0.01 0.0001 0.3 1 10 OUTPUT SWING (VP-P) 30 1677 G27 LT1677 APPLICATIO S I FOR ATIO General INPUT 3 Rail-to-Rail Operation To take full advantage of an input range that can exceed the supply, the LT1677 is designed to eliminate phase reversal. Referring to the photographs shown in Figure 1, the LT1677 is operating in the follower mode (AV = +1) at a single 3V supply. The output of the LT1677 clips cleanly and recovers with no phase reversal. This has the benefit of preventing lock-up in servo systems and minimizing distortion components. Offset Voltage Adjustment The input offset voltage of the LT1677 and its drift with temperature are permanently trimmed at wafer testing to a low level. However, if further adjustment of VOS is necessary, the use of a 10kΩ nulling potentiometer will not degrade drift with temperature. Trimming to a value other than zero creates a drift of (VOS / 300)µV/ °C, e.g., if VOS is adjusted to 300µV, the change in drift will be 1µV/ °C (Figure 2). 4.7k Figure 2. Standard Adjustment The adjustment range with a 10kΩ pot is approximately ± 2.5mV. If less adjustment range is needed, the sensitivity and resolution of the nulling can be improved by using a smaller pot in conjunction with fixed resistors. The example has an approximate null range of ± 200µV (Figure 3). 1k 15V 1 Figure 3. Improved Sensitivity Adjustment Input = – 0.5V to 3.5V 3V 3V 2V 2V 1V 1V 0V – 0.5V 1577 F01a 0V – 0.5V 1577 F01b Figure 1. Voltage Follower with Input Exceeding the Supply Voltage (VS = 3V) + 3 – 2 LT1677 4 LT1677 Output + – The LT1677 series devices may be inserted directly into OP-07, OP-27, OP-37 and sockets with or without removal of external compensation or nulling components. In addition, the LT1677 may be fitted to 741 sockets with the removal or modification of external nulling components. U 10k 15V 1 2 8 7 6 OUTPUT LT1677 4 –15V 1677 F02 W UU 4.7k 8 76 OUTPUT –15V 1677 F03 9 LT1677 APPLICATIO S I FOR ATIO Offset Voltage and Drift Thermocouple effects, caused by temperature gradients across dissimilar metals at the contacts to the input terminals, can exceed the inherent drift of the amplifier unless proper care is exercised. Air currents should be minimized, package leads should be short, the two input leads should be close together and maintained at the same temperature. The circuit shown to measure offset voltage is also used as the burn-in configuration for the LT1677, with the supply voltages increased to ± 20V (Figure 4). 50k* 15V Noise Testing 7 6 VOUT 50k* –15V Figure 4. Test Circuit for Offset Voltage and Offset Voltage Drift with Temperature Unity-Gain Buffer Application When RF ≤ 100Ω and the input is driven with a fast, largesignal pulse (>1V), the output waveform will look as shown in the pulsed operation diagram (Figure 5). During the fast feedthrough-like portion of the output, the input protection diodes effectively short the output to the input and a current, limited only by the output short-circuit protection, will be drawn by the signal generator. With RF ≥ 500Ω, the output is capable of handling the current requirements (IL ≤ 20mA at 10V) and the amplifier stays in its active mode and a smooth transition will occur. As with all operational amplifiers when RF > 2k, a pole will be created with RF and the amplifier’s input capacitance, 10 + 100Ω* 3 – 2 LT1677 4 VOUT = 1000VOS *RESISTORS MUST HAVE LOW THERMOELECTRIC POTENTIAL 1677 F04 The 0.1Hz to 10Hz peak-to-peak noise of the LT1677 is measured in the test circuit shown (Figure 6a). The frequency response of this noise tester (Figure 6b) indicates that the 0.1Hz corner is defined by only one zero. The test time to measure 0.1Hz to 10Hz noise should not exceed ten seconds, as this time limit acts as an additional zero to eliminate noise contributions from the frequency band below 0.1Hz. Measuring the typical 70nV peak-to-peak noise performance of the LT1677 requires special test precautions: 1. The device should be warmed up for at least five minutes. As the op amp warms up, its offset voltage changes typically 3µV due to its chip temperature increasing 10°C to 20°C from the moment the power supplies are turned on. In the ten-second measurement interval these temperature-induced effects can easily exceed tens of nanovolts. 2. For similar reasons, the device must be well shielded from air currents to eliminate the possibility of thermoelectric effects in excess of a few nanovolts, which would invalidate the measurements. 3. Sudden motion in the vicinity of the device can also “feedthrough” to increase the observed noise. – + U creating additional phase shift and reducing the phase margin. A small capacitor (20pF to 50pF) in parallel with RF will eliminate this problem. RF 2.5V/µs OUTPUT LT1677 1677 F05 W UU Figure 5. Pulsed Operation LT1677 APPLICATIO S I FOR ATIO 0.1µF 100k GAIN (dB) VOLTAGE GAIN = 50,000 *DEVICE UNDER TEST NOTE: ALL CAPACITOR VALUES ARE FOR NONPOLARIZED CAPACITORS ONLY 24.3k Current noise is measured in the circuit shown in Figure 7 and calculated by the following formula: 2  2  eno − 130nV • 101   in =  1MΩ 101 Figure 7 1000 R TOTAL NOISE DENSITY (nV/√Hz) The LT1677 achieves its low noise, in part, by operating the input stage at 120µA versus the typical 10µA of most other op amps. Voltage noise is inversely proportional while current noise is directly proportional to the square root of the input stage current. Therefore, the LT1677’s current noise will be relatively high. At low frequencies, the low 1/f current noise corner frequency (≈ 90Hz) minimizes current noise to some extent. In most practical applications, however, current noise will not limit system performance. This is illustrated in the Total Noise vs Source Resistance plot (Figure 8) where: Total Noise = [(voltage noise)2 + (current noise • RS)2 + (resistor noise)2]1/2 Three regions can be identified as a function of source resistance: (i) RS ≤ 400Ω. Voltage noise dominates (ii) 400Ω ≤ RS ≤ 50k at 1kHz 400Ω ≤ RS ≤ 8k at 10Hz R SOURCE RESISTANCE = 2R 100 10 RESISTOR NOISE ONLY 1 0.1 1 10 SOURCE RESISTANCE (kΩ) 100 1677 F08 Figure 8. Total Noise vs Source Resistance (iii) RS > 50k at 1kHz RS > 8k at 10Hz } Current noise dominates } Resistor noise dominates Clearly the LT1677 should not be used in region (iii), where total system noise is at least six times higher than the + ) ()( ( )( ) 1/ 2 500k – + – 10Ω * LT1677 2k 4.7µF + LT1001 – 100k 0.1µF Figure 6a. 0.1Hz to 10Hz Noise Test Circuit U 100 90 80 70 60 50 40 30 0.01 1677 F06a W UU 4.3k 22µF 2.2µF SCOPE ×1 RIN = 1M 110k 0.1 1 10 FREQUENCY (Hz) 100 1677 F06b Figure 6b. 0.1Hz to 10Hz Peak-to-Peak Noise Tester Frequency Response 100k 100Ω 500k LT1677 eno 1677 F07 VS = ± 15V TA = 25°C AT 1kHz AT 10Hz 11 LT1677 APPLICATIO S I FOR ATIO voltage noise of the op amp, i.e., the low voltage noise specification is completely wasted. In this region the LT1792 or LT1793 is the best choice. Rail-to-Rail Input The LT1677 has the lowest voltage noise, offset voltage and highest gain when compared to any rail-to-rail op amp. The input common mode range for the LT1677 can exceed the supplies by at least 100mV. As the common mode voltage approaches the positive rail (VCC – 0.7V), the tail current for the input pair (Q1, Q2) is reduced, which prevents the input pair from saturating (refer to the Simplified Schematic). The voltage drop across the load TYPICAL APPLICATIO Microvolt Comparator with Hysteresis INPUT POSITIVE FEEDBACK TO ONE OF THE NULLING TERMINALS CREATES APPROXIMATELY 5µV OF HYSTERESIS. OUTPUT CAN SINK 16mA INPUT OFFSET VOLTAGE IS TYPICALLY CHANGED LESS THAN 5µV DUE TO THE FEEDBACK 12 – 2 + U resistors RC1, RC2 is reduced to less than 200mV, degrading the slew rate, bandwidth voltage noise, offset voltage and input bias current (the cancellation is shut off). When the input common mode range goes below 1.5V above the negative rail, the NPN input pair (Q1, Q2) shuts off and the PNP input pair (Q8, Q9) turns on. The offset voltage, input bias current, voltage noise and bandwidth are also degraded. The graph of Offset Voltage vs Common Mode Range shows where the knees occur by displaying the change in offset voltage. The change-over points are temperature dependent, see Common Mode Range vs Temperature. 10M 5% 3 7 8 LT1677 4 –15V 1677 TA02 W U UU 365Ω 1% 15k 1% 15V 6 OUTPUT V+ RC1B 1k C10 81pF PAD 8 200µA Q32 Q35 Q34 RC2A 4.5k RC1A 4.5k RC2B 1k R32 1.5k R34 2k Q28 SI PLIFIED SCHE ATIC W Q17 Q18 R2 50Ω R1 500Ω C1 40pF 100µA + Q4 R19 2k R20 2k Q20 Q10 Q11 Q6 Q7 C2 80pF + OUT Q12 Q5 Q27 C3 40pF Q23 R3 100Ω D4 Q3 D2 100µA D1 D3 160µA Q31 + –IN Q19 Q1A Q1B Q2A Q2B IA R9 200Ω 50µA 50µA IB Q22 Q30 Q26 R54 100Ω Q29 R23A 10k R8 200Ω Q13 ×2 IC ID Q21 Q24 Q8 Q9 Q15 Q14 Q16 Q25 R30 2k R26 100Ω Q38 R23B 10k R15 1k R14 1k R16 1k R25 1k R29 10Ω R13 100Ω R21 100Ω R24 100Ω IA, IB = 200µA VCM > 1.5V ABOVE VEE 0µA VCM < 1.5V ABOVE VEE IC = 200µA VCM < 0.7V BELOW VCC ID = 100µA VCM < 0.7V BELOW VCC 50µA VCM > 0.7V BELOW VCC 0µA VCM > 0.7V BELOW VCC 1677 SS + +IN C4 20pF V– W + PAD 1 LT1677 13 LT1677 PACKAGE DESCRIPTIO 0.300 – 0.325 (7.620 – 8.255) 0.009 – 0.015 (0.229 – 0.381) ( +0.035 0.325 –0.015 8.255 +0.889 –0.381 ) *THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm) 14 U Dimensions in inches (millimeters) unless otherwise noted. N8 Package 8-Lead PDIP (Narrow 0.300) (LTC DWG # 05-08-1510) 0.400* (10.160) MAX 8 7 6 5 0.255 ± 0.015* (6.477 ± 0.381) 1 2 3 4 0.130 ± 0.005 (3.302 ± 0.127) 0.045 – 0.065 (1.143 – 1.651) 0.065 (1.651) TYP 0.125 (3.175) 0.020 MIN (0.508) MIN 0.018 ± 0.003 (0.457 ± 0.076) N8 1098 0.100 (2.54) BSC LT1677 PACKAGE DESCRIPTIO U Dimensions in inches (millimeters) unless otherwise noted. S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.189 – 0.197* (4.801 – 5.004) 8 7 6 5 0.228 – 0.244 (5.791 – 6.197) 0.150 – 0.157** (3.810 – 3.988) 1 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 0°– 8° TYP 2 3 4 0.053 – 0.069 (1.346 – 1.752) 0.004 – 0.010 (0.101 – 0.254) 0.014 – 0.019 (0.355 – 0.483) TYP *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE 0.016 – 0.050 (0.406 – 1.270) 0.050 (1.270) BSC SO8 1298 15 LT1677 TYPICAL APPLICATIO U gain of ~107. Components R5 and Q1 convert the voltage into a current for transmission back to R10, which converts it into a voltage again. The LM334 and 2N3904 are not temperature compensated so the DC output contains temperature information. 2-Wire Remote Geophone Preamp R9 20Ω LINEAR TECHNOLOGY LM334Z 6mA V+ R V– R8 11Ω Q1 2N3904 12V R4 14k R1 150Ω GEOSOURCE MD-105 RL = 847Ω GEOPHONE R2 100k This 2-wire remote Geophone preamp operates on a current-loop principle and so has good noise immunity. Quiescent current is ≈ 10mA for a VOUT of 2.5V. Excitation will cause AC currents about this point of ~ ± 4mA for a VOUT of ~ ± 1V max. The op amp is configured for a voltage 3V C LT1431CZ A R R6 4.99k R7 24.9k + C3 220µF – + R3 16.2k 3 AV = R2 + R3||R4 R1 + RL ≅ 107 RELATED PARTS PART NUMBER LT1028 LT1115 LT1124/LT1125 LT1126/LT1127 LT1498/LT1499 LT1792 LT1793 LT1884 DESCRIPTION Ultralow Noise Precision Op Amp Ultralow Noise, Low distortion Audio Op Amp Dual/Quad Low Noise, High Speed Precision Op Amps Dual/Quad Decompensated Low Noise, High Speed Precision Op Amps 10MHz, 5V/µs, Dual/Quad Rail-to-Rail Input and Output Op Amps Low Noise, Precision JFET Input Op Amp Low Noise, Picoampere Bias Current Op Amp Dual Rail-to-Rail Output Picoamp Input Precision Op Amp COMMENTS Lowest Noise 0.85nV/√Hz 0.002% THD, Max Noise 1.2nV/√Hz Similar to LT1007 Similar to LT1037 Precision C-LoadTM Stable 4.2nV/√Hz, 10fA/√Hz 6nV/√Hz, 1fA/√Hz 2.2MHz Bandwidth, 1.2V/µs SR C-Load is a trademark of Linear Technology Corporation. 16 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900 q FAX: (408) 434-0507 q www.linear-tech.com + – 2 7 LT1677 4 6 C2 0.1µF R5 243Ω R10 250Ω VOUT 2.5V ± 1V C4 1000pF 1677 TA03 1677i LT/TP 0200 4K • PRINTED IN USA © LINEAR TECHNOLOGY CORPORATION 2000