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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: 60V Max Low VOS Drift: 0.2V/C Typ Low Input Bias Current: 20nA Max Wide Supply Range: 3V to 15V High AVOL: 4V/V Min, RL = 1k High CMRR: 109dB Min High PSRR: 108dB Min Gain Bandwidth Product: 7.2MHz Slew Rate: 2.5V/s Operating Temperature Range: - 40C to 85C
APPLICATIO S
s s s s s s
The LT (R)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: 20V offset voltage and 0.2V/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 0.1
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) ............................. - 40C to 85C LT1677I ............................................. - 40C to 85C Specified Temperature Range LT1677C (Note 5) ............................. - 40C to 85C LT1677I ............................................. - 40C to 85C
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 ................. - 65C to 150C Lead Temperature (Soldering, 10 sec.)................. 300C
PACKAGE/ORDER I FOR ATIO
TOP VIEW VOS TRIM 1 -IN 2 +IN 3 V- 4 N8 PACKAGE 8-LEAD PDIP TJMAX = 150C, JA = 130C/ 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 = 25C, 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 V V mV V/Mo nA A A 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
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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 = 150C, JA = 190C/ 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 600, 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 = 25C, 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 G pF pF dB dB dB dB V/V V/V V/V
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/V V/V mV mV mV mV mV mV mA V/s MHz % s s 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 0C < TA < 70C. 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 600, 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 V V mV V/C V/C nA A A nA nA nA V dB dB dB dB V/V V/V V/V
-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/V V/V mV mV mV mV mV mV mA V/s 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 - 40C < TA < 85C. 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 600, 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 V V mV V/C V/C nA A A nA nA nA V dB dB dB dB V/V V/V V/V
- 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/V V/V mV mV mV mV mV mV mA V/s 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 - 40C to 85C. Note 5: The LT1677C is guaranteed to meet specified performance from 0C to 70C. The LT1677C is designed, characterized and expected to
meet specified performance from -40C to 85C 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 = 25C 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 = 25C
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 (V)
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 250 200 150
PERCENT OF UNITS (%)
OFFSET VOLTAGE CHANGE (V)
OFFSET VOLTAGE (mV)
1.0 0.5 0 -0.5 -1.0 -1.5 -2.0
125C 25C -55C -55C
VOS IS REFERRED 125C 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 = 25C 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 (V)
-2.5 -1.0 VEE
1.0
-150 VS = 1.5V TO 15V TA = 25C -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 = -40C TO 85C 120 PARTS (2 LOTS) 5 4 3 2 1 0 -1 -2 -3 -4 -5
Long-Term Stability of Four Representative Units
OFFSET VOLTAGE (V)
100 50 0 -50 25C -100 -150 -200 0.4
1677 G09
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 (V/C)
1677 G02
-250
0 100 200 300 400 500 600 700 800 900 TIME (HOURS)
1677 G13
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 = 125C 3 TA = 25C
2
TA = -55C
1 0
5 10 15 SUPPLY VOLTAGE (V)
Voltage Gain vs Frequency
180 VS = 15V TA = 25C 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/s)
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 = 25C 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 = 25C
20
1677 G15
Gain, Phase Shift vs Frequency
50 40 VS = 15V VCM = 0V TA = 25C 80 CL = 10pF 100
60 50
Overshoot vs Load Capacitance
VS = 15V TA = 25C 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 (s)
VIN
VIN
RL = 1k
8 6 4 2 VS = 15V AV = -1 TA = 25C 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 (s)
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 125C VS = 15V 100 -55C
Closed-Loop Output Impedance vs Frequency
TOTAL HARMONIC DISTROTION + NOISE (%)
OUTPUT IMPEDANCE ()
25C
10
1 AV = +100 0.1 AV = +1 0.01
-30 -35 -40 -45 -50 0 3 2 4 1 TIME FROM OUTPUT SHORT TO GND (MIN)
1677 G23
125C -55C
25C
0.001
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 = 25C
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 125C 0.4 25C 0.3 0.2 -55C 0.1 V- 0 -10 -8 -6 -4 -2 0 2 4 6 8 ISOURCE ISINK OUTPUT CURRENT (mA) 10 -55C
25C 125C
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 10k nulling potentiometer will not degrade drift with temperature. Trimming to a value other than zero creates a drift of (VOS / 300)V/C, e.g., if VOS is adjusted to 300V, the change in drift will be 1V/C (Figure 2).
4.7k
Figure 2. Standard Adjustment
The adjustment range with a 10k 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 200V (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 100 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 500, 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
+
100* 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 3V due to its chip temperature increasing 10C to 20C 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/s OUTPUT LT1677
1677 F05
W
UU
Figure 5. Pulsed Operation
LT1677
APPLICATIO S I FOR ATIO
0.1F 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 = 1M 101
Figure 7
1000
R
TOTAL NOISE DENSITY (nV/Hz)
The LT1677 achieves its low noise, in part, by operating the input stage at 120A versus the typical 10A 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 400. Voltage noise dominates (ii) 400 RS 50k at 1kHz 400 RS 8k at 10Hz
R SOURCE RESISTANCE = 2R
100
10 RESISTOR NOISE ONLY 1 0.1 1 10 SOURCE RESISTANCE (k) 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
-
+
-
10
* LT1677
2k
+
LT1001
4.7F
-
100k 0.1F
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
22F
SCOPE x1 RIN = 1M 110k
2.2F
0.1
1 10 FREQUENCY (Hz)
100
1677 F06b
Figure 6b. 0.1Hz to 10Hz Peak-to-Peak Noise Tester Frequency Response
100k
100
500k
LT1677
eno
1677 F07
VS = 15V TA = 25C
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 5V OF HYSTERESIS. OUTPUT CAN SINK 16mA INPUT OFFSET VOLTAGE IS TYPICALLY CHANGED LESS THAN 5V 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.
15V 10M 5% 3 7 8 LT1677 4 -15V
1677 TA02
W
U
UU
365 1% 15k 1% OUTPUT
6
V+
RC1B 1k C10 81pF PAD 8 200A 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 50 100A
R1 500
C1 40pF
+
Q4 R19 2k R20 2k Q20 Q10 Q11 Q6 Q7 C2 80pF
+
OUT
Q12
Q5
Q27 C3 40pF Q23 R3 100
D4 Q3 D2 100A
D1
D3
160A
Q31
+
-IN Q19
Q1A Q1B Q2A
Q2B
IA R9 200 50A 50A
IB Q22
Q30 Q26
R54 100 Q29 R23A 10k
R8 200
Q13 x2 IC ID
Q21
Q24
Q8
Q9
Q15
Q14
Q16
Q25
R30 2k
R26 100
Q38 R23B 10k R15 1k R14 1k R16 1k R25 1k R29 10
R13 100
R21 100
R24 100
IA, IB = 200A VCM > 1.5V ABOVE VEE 0A VCM < 1.5V ABOVE VEE
IC = 200A VCM < 0.7V BELOW VCC ID = 100A VCM < 0.7V BELOW VCC 50A VCM > 0.7V BELOW VCC 0A 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 x 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 20 LINEAR TECHNOLOGY LM334Z 6mA V+ R V- R8 11 Q1 2N3904 12V R4 14k R1 150 GEOSOURCE MD-105 RL = 847 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 220F
- +
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/s, 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/s 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 0.1F
R5 243 R10 250
VOUT 2.5V 1V
C4 1000pF
1677 TA03
1677i LT/TP 0200 4K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 2000

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