LINER LT1677I Low noise, rail-to-rail precision op amp Datasheet

Final Electrical Specifications
LT1677
Low Noise, Rail-to-Rail
Precision Op Amp
February 2000
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FEATURES
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DESCRIPTIO
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
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.
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APPLICATIO S
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, 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
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TYPICAL APPLICATIO
Precision High Side Current Sense
SOURCE
RIN
1k
RLINE
0.1Ω
2
–
3
+
7
LT1677
4
LOAD
6
ZETEX
BC856B
VOUT
ROUT
VOUT
ROUT
20k
ILOAD = RLINE RIN
= 2V/AMP
1677 TA01
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.
1
LT1677
W W
W
AXI U
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ABSOLUTE
RATI GS (Note 1)
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
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
U
U
W
PACKAGE/ORDER I FOR ATIO
TOP VIEW
VOS
TRIM 1
–IN 2
+IN 3
VOS
8 TRIM
–
+
V– 4
7
V+
6
OUT
5
NC
ORDER PART
NUMBER
LT1677CN8
LT1677IN8
ORDER PART
NUMBER
TOP VIEW
VOS
1
TRIM
–IN 2
+IN 3
V– 4
8
VOS
TRIM
–
7
V+
+
6
OUT
5
NC
N8 PACKAGE
8-LEAD PDIP
S8 PACKAGE
8-LEAD PLASTIC SO
TJMAX = 150°C, θJA = 130°C/ W
TJMAX = 150°C, θJA = 190°C/ W
LT1677CS8
LT1677IS8
S8 PART MARKING
1677
1677I
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
VOS
Input Offset Voltage
TA = 25°C, VS = ±15V, VCM = VO = 0V unless otherwise noted.
CONDITIONS (Note 6)
MIN
VCM = 14V to 15.1V
VCM = –13.3V to –15.1V
∆VOS
∆Time
Long Term Input Voltage Stability
IB
Input Bias Current
en
2
MAX
UNITS
20
150
1.5
60
400
5
µV
µV
mV
µV/Mo
0.3
±2
0.16
– 0.4
±20
0.4
nA
µA
µA
VCM = 14V to 15.1V
VCM = –13.3V to –15.1V
3
5
20
15
25
200
nA
nA
nA
Input Noise Voltage
0.1Hz to 10Hz (Note 7)
VCM = 15V
VCM = –15V
70
33
100
nVP-P
nVP-P
nVP-P
Input Noise Voltage Density
VCM = 0V, fO = 10Hz
VCM = 15V, fO = 10Hz
VCM = –15V, fO = 10Hz
5.2
25
7
nV/√Hz
nV/√Hz
nV/√Hz
VCM = 0V, fO = 1kHz (Note 8)
VCM = 15V, fO = 1kHz
VCM = –15V, fO = 1kHz
3.2
17
5.3
VCM = 14V to 15.1V
VCM = –13.3V to –15.1V
IOS
TYP
Input Offset Current
– 1.5
4.5
nV/√Hz
nV/√Hz
nV/√Hz
LT1677
ELECTRICAL CHARACTERISTICS
TA = 25°C, VS = ±15V, VCM = VO = 0V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS (Note 6)
in
Input Noise Current Density
fO = 10Hz
fO = 1kHz
VCM
Input Voltage Range
RIN
Input Resistance
CIN
Input Capacitance
CMRR
Common Mode Rejection Ratio
VCM = –13.3V to 14.0V
VCM = ±15.1V
PSRR
Power Supply Rejection Ratio
AVOL
Large-Signal Voltage Gain
VOL
VOH
Output Voltage Swing Low
Output Voltage Swing High
ISC
Output Short-Circuit Current (Note 3)
SR
Slew Rate
GBW
THD
MIN
TYP
MAX
1.2
0.3
±15.1
Common Mode
UNITS
pA/√Hz
pA/√Hz
±15.2
V
2
GΩ
3.8
4.2
pF
pF
109
74
130
95
dB
dB
VS = ±1.7V to ±18V
VS = 2.7V to 40V, VCM = VO = 1.7V
106
108
130
125
dB
dB
RL ≥ 10k, VO = ±14V
RL ≥ 1k, VO = ±13.5V
RL ≥ 600Ω, VO = ±10V
7
4
0.4
25
20
0.7
V/µV
V/µV
V/µV
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
2
1.5
10
4
V/µV
V/µV
VS = ±2.5V
Above VEE
ISINK = 0.1mA
ISINK = 2.5mA
ISINK = 10mA
80
110
300
170
250
500
mV
mV
mV
Below VCC
ISOURCE = 0.1mA
ISOURCE = 2.5mA
ISOURCE = 10mA
110
190
500
170
300
700
mV
mV
mV
25
35
mA
RL ≥ 10k (Note 9)
1.7
2.5
V/µs
Gain Bandwidth Product
fO = 100kHz
4.5
7.2
MHz
Total Harmonic Distortion
RL = 2k, AV = 1, fO = 1kHz, VO = 10VP-P
tS
Settling Time
RO
Open-Loop Output Resistance
Closed-Loop Output Resistance
IS
Supply Current
0.0006
%
10V Step 0.1%, AV = +1
10V Step 0.01%, AV = +1
5
6
µs
µs
IOUT = 0
AV = 100, f = 10kHz
80
1
Ω
Ω
2.75
3.5
mA
3
LT1677
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the temperature range of
0°C < TA < 70°C. VS = ±15V, VCM = VO = 0V unless otherwise noted.
SYMBOL
PARAMETER
VOS
Input Offset Voltage
∆VOS
∆Temp
Average Input Offset Drift
IB
Input Bias Current
IOS
Input Voltage Range
CMRR
Common Mode Rejection Ratio
PSRR
AVOL
VOH
TYP
MAX
UNITS
VCM = 14.0V to 14.8V
VCM = –13.3V to –15V
●
●
●
30
180
1.8
120
550
6
µV
µV
mV
SO-8
N8 (Note 10)
●
●
0.40
0.20
2
0.5
µV/°C
µV/°C
VCM = 14.0V to 14.8V
VCM = –13.3V to –15V
●
●
●
±3
0.19
– 0.43
±35
0.6
nA
µA
µA
VCM = 14.0V to 14.8V
VCM = –13.3V to –15V
●
●
●
2
90
90
20
220
350
nA
nA
nA
14.8
V
Input Offset Current
VCM
VOL
CONDITIONS (Note 6)
MIN
–2
●
–15
VCM = –13.3V to 14.0V
VCM = –15V to 14.8V
●
●
106
73
126
93
dB
dB
Power Supply Rejection Ratio
VS = ±1.7V to ±18V
VS = 2.8V to 40V, VCM = VO = 1.7V
●
●
104
106
127
122
dB
dB
Large-Signal Voltage Gain
RL ≥ 10k, VO = ±14V
RL ≥ 1k, VO = ±13.5V
RL ≥ 600Ω, VO = ±10V
●
●
●
4
2
0.3
20
10
0.5
V/µV
V/µV
V/µV
VCC = 5V or 3V, VEE = 0V, VCM = 1.7V,
VOUT = 0.4V to:
RL ≥ 10k, VCC – 0.5V
RL ≥ 1k, VCC – 0.7V
●
●
3
0.5
8
4
V/µV
V/µV
Above VEE
ISINK = 0.1mA
ISINK = 2.5mA
ISINK = 10mA
●
●
●
85
160
400
200
320
600
mV
mV
mV
Below VCC
ISOURCE = 0.1mA
ISOURCE = 2.5mA
ISOURCE = 10mA
●
●
●
140
230
580
200
350
800
mV
mV
mV
Output Voltage Swing Low
Output Voltage Swing High
ISC
Output Short-Circiut Current (Note 3)
●
20
27
mA
SR
Slew Rate
RL ≥ 10k (Note 9)
●
1.5
2.3
V/µs
GBW
Gain Bandwidth Product
fO = 100kHz
●
6.2
MHz
IS
Supply Current
●
3.0
4
3.9
mA
LT1677
ELECTRICAL CHARACTERISTICS
The ● 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
PARAMETER
VOS
Input Offset Voltage
∆VOS
∆Temp
Average Input Offset Drift
IB
Input Bias Current
IOS
Input Voltage Range
CMRR
Common Mode Rejection Ratio
PSRR
AVOL
VOH
TYP
MAX
UNITS
VCM = 14.0V to 14.7V
VCM = –13.3V to –15V
●
●
●
45
200
2
180
650
6.5
µV
µV
mV
SO-8
N8 (Note 10)
●
●
0.40
0.20
2.0
0.5
µV/°C
µV/°C
VCM = 14.0V to 14.7V
VCM = –13.3V to –15V
●
●
●
±7
0.25
– 0.45
±50
0.75
nA
µA
µA
VCM = 14.0V to 14.7V
VCM = –13.3V to –15V
●
●
●
6
100
100
40
250
400
nA
nA
nA
14.7
V
Input Offset Current
VCM
VOL
CONDITIONS (Note 6)
MIN
– 2.3
●
–15
VCM = –13.3V to 14.0V
VCM = –15V to 14.7V
●
●
105
72
124
91
dB
dB
Power Supply Rejection Ratio
VS = ±1.7V to ±18V
VS = 3.1V to 40V, VCM = VO = 1.7V
●
●
103
105
125
120
dB
dB
Large-Signal Voltage Gain
RL ≥ 10k, VO = ±14V
RL ≥ 1k, VO = ±13.5V
RL ≥ 600Ω, VO = ±10V
●
●
●
3
1.5
0.2
17
8
0.35
V/µV
V/µV
V/µV
VCC = 5V or 3V, VEE = 0V, VCM = 1.7V,
VOUT = 0.5V to:
RL ≥ 10k, VCC – 0.5V
RL ≥ 1k, VCC – 0.7V
●
●
2
0.2
15
2
V/µV
V/µV
Above VEE
ISINK = 0.1mA
ISINK = 2.5mA
ISINK = 10mA
●
●
●
90
175
450
230
350
650
mV
mV
mV
Below VCC
ISOURCE = 0.1mA
ISOURCE = 2.5mA
ISOURCE = 10mA
●
●
●
150
250
600
250
375
850
mV
mV
mV
Output Voltage Swing Low
Output Voltage Swing High
ISC
Output Short-Circuit Current (Note 3)
●
18
25
mA
SR
Slew Rate
RL ≥ 10k (Note 9)
●
1.2
2.0
V/µs
GBW
Gain Bandwidth Product
fO = 100kHz
●
5.8
MHz
IS
Supply Current
●
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
4.0
mA
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
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TYPICAL PERFOR A CE CHARACTERISTICS
Voltage Noise vs Frequency
Current Noise vs Frequency
RMS CURRENT NOISE DENSITY (pA/√Hz)
VCM > 14.5V
1/f CORNER 8.5Hz
10
VCM < –14.5V
1/f CORNER 13Hz
VS = ±15V
TA = 25°C
1
0.1
VCM < –13.5V
1/f CORNER 180Hz
1
VCM
–13.5V TO 14.5V
1/f CORNER 90Hz
1/f CORNER 60Hz
VCM > 14.5V
0.1
1
10
100
FREQUENCY (Hz)
100
1000
FREQUENCY (Hz)
10
1000
800
OFFSET VOLTAGE (mV)
VCM = 15.15V
INPUT BIAS CURRENT
0
VCM = 14.3V
–200
VCM = –15.3V
–400
–600
140
120
1.0
50
0
0
–0.5
–50
–1.0
–100
–1.5
–150
VS = ±1.5V TO ±15V
TA = 25°C
–200
5 TYPICAL PARTS
–250
2.0 –0.8 –0.4 VCC 0.4
VCM – VEE (V)
20
200
18
150
16
100
–55°C
–55°C
50
0
0
–0.5
–50
–100
25°C
OFFSET VOLTAGE (µV)
125°C
250
40
20
0
–20
–40
–60
–80
–55 –35 –15
VCM – VCC (V)
Long-Term Stability of Four
Representative Units
VS = ±15V
TA = –40°C TO 85°C
120 PARTS
(2 LOTS)
14
12
10
8
6
5
4
3
2
1
0
–1
–2
–3
4
–2.0
–200
2
–4
–250
0
–0.25 –0.15 –0.05 0.05 0.15 0.25 0.35 0.45
INPUT OFFSET VOLTAGE DRIFT (µV/°C)
–5
VCM – VEE (V)
2.0 –0.8 –0.4 VCC
0.4
VCM – VCC (V)
1677 G09
6
5 25 45 65 85 105 125
TEMPERATURE (°C)
1677 G11
–150
1.0
125
60
–1.5
–2.5
–1.0 VEE
100
VS = ±15V
VCM = 0V
SO-8
N8
1677 G08
PERCENT OF UNITS (%)
1.5
OFFSET VOLTAGE (mV)
80
Distribution of Input Offset
Voltage Drift (N8)
VS = ±2.5V TO ±15V
VOS IS REFERRED 125°C
TO VCM = 0V
100
0.5
1.0
100
150
VOS IS REFERRED
TO VCM = 0V
–2.5
–1.0 VEE
16
2.0
50
25
0
75
TEMPERATURE (°C)
VOS vs Temperature of
Representative Units
200
Common Mode Range
vs Temperature
–1.0
3
250
1677 G06
25°C
1kHz
2.0
–2.0
–800
0
4
–16 –12 –8 –4
8
12
COMMON MODE INPUT VOLTAGE (V)
0.5
4
2.5
1.5
400
1.0
5
1677 G05
OFFSET VOLTAGE (µV)
INPUT BIAS CURRENT (nA)
VS = ±15V
600 TA = 25°C
2.5
10Hz
Offset Voltage Shift
vs Common Mode
Input Bias Current Over the
Common Mode Range
200
6
1677 G04
1677 G03
VCM = –13.6V
VS = ±15V
VCM = 0V
2
–50 –25
10000
VOLTAGE OFFSET (µV)
VCM
–13.5V TO 14.5V
VS = ±15V
TA = 25°C
OFFSET VOLTAGE CHANGE (µV)
RMS VOLTAGE NOISE DENSITY (nV/√Hz)
1/f CORNER 10Hz
Voltage Noise vs Temperature
7
RMS VOLTAGE NOISE DENSITY (nV/√Hz)
10
100
1677 G02
0 100 200 300 400 500 600 700 800 900
TIME (HOURS)
1677 G13
LT1677
U W
TYPICAL PERFOR A CE CHARACTERISTICS
160
TA = 125°C
3
TA = 25°C
TA = –55°C
1
±5
±10
±15
SUPPLY VOLTAGE (V)
0
120
100
80
60
40
20
0
±20
1k
10k
100k
1M
FREQUENCY (Hz)
Voltage Gain vs Frequency
VOLTAGE GAIN (dB)
VOLTAGE GAIN (dB)
VCM = VCC
20
10k
100
FREQUENCY (Hz)
1M
40
10
20
0
0
10
–20
100
0
0.1
PHASE MARGIN (DEG)
8
7
SLEW RATE (V/µs)
6
5
4
2
1
–50 –25
50
25
0
75
TEMPERATURE (°C)
100
GAIN BANDWIDTH PRODUCT, fO = 100kHz (MHz)
60
SLEW
100k
1
10
FREQUENCY (MHz)
10V
1M
RISING
EDGE
30
20
FALLING
EDGE
10
100
CAPACITANCE (pF)
1000
1677 G30
1677 G17
VS = ±15V
CL = 15pF
3
10k
1k
FREQUENCY (Hz)
VS = ±15V
TA = 25°C
RL = 10k TO 2k
Small-Signal Transient Response
Large-Signal Transient Response
GBW
100
40
20
100M
50
10
1
50
60
PM, GBWP, SR vs Temperature
PHASE
20
30
1677 G16
70
40
Overshoot vs Load Capacitance
VS = ±15V
VCM = 0V
TA = 25°C 80
CL = 10pF
–10
1
POSITIVE SUPPLY
60
60
PHASE SHIFT (DEG)
VCM = 0V
–20
0.01
NEGATIVE SUPPLY
80
1677 G15
100
40
140
VCM = VEE
100
Gain, Phase Shift vs Frequency
50
VS = ±15V
TA = 25°C
60
120
1677 G14
1677 G28
100
VS = ±15V
TA = 25°C
140
0
10M
OVERSHOOT (%)
2
160
VS = ±15V
140 TA = 25°C
VEM = 0V
POWER SUPPLY REJECTION RATIO (dB)
COMMON MODE REJECTION RATIO (dB)
SUPPLY CURRENT (mA)
4
180
Power Supply Rejection Ratio
vs Frequency
Common Mode Rejection Ratio
vs Frequency
Supply Current vs Supply Voltage
50mV
0
– 50mV
– 10V
AVCL = – 1
VS = ±15V
AVCL = 1
VS = ±15V
CL = 15pF
125
1677 G29
7
LT1677
U W
TYPICAL PERFOR A CE CHARACTERISTICS
SETTLING TIME (µs)
10
12
5k
–
VIN
0.1% OF
FULL SCALE
6
0.01% OF
FULL SCALE
0.1% OF
FULL SCALE
4
10
VOUT
+
8
0
–10 –8 –6 –4 –2 0 2 4
OUTPUT STEP (V)
6
8
–
2k
VIN
2k
RL = 1k
8
0.01% OF
FULL SCALE
6
0.01% OF
FULL SCALE
4
0.1% OF
FULL SCALE
0
–10 –8 –6 –4 –2 0 2 4
OUTPUT STEP (V)
10
VOUT
+
0.1% OF
2 FULL SCALE
VS = ±15V
AV = –1
TA = 25°C
2
VS = ±15V
AV = 1
TA = 25°C
5k
6
100
25°C
20
125°C
10
–30
–35
125°C
–40
25°C
10
1
AV = +100
0.1
AV = +1
0.01
–55°C
–45
–50
0.001
0
3
2
4
1
TIME FROM OUTPUT SHORT TO GND (MIN)
AV = –100
0.001
AV = –10
AV = –1
0.0001
20
100
1k
FREQUENCY (Hz)
10k 20k
1677 G25
8
ZL = 2k/15pF
VO = 20VP-P
AV = +1, +10, +100
MEASUREMENT BANDWIDTH
= 10Hz TO 80kHz
0.01
AV = 100
0.001
AV = 10
AV = 1
100
10k
1k
FREQUENCY (Hz)
100k
1M
20
100
1k
FREQUENCY (Hz)
1
Total Harmonic Distortion and
Noise vs Output Amplitude for
Inverting Gain
ZL = 2k/15pF
fO = 1kHz
AV = +1, +10, +100
MEASUREMENT BANDWIDTH
= 10Hz TO 22kHz
0.1
AV = 100
0.01
AV = 10
AV = 1
0.001
0.0001
0.3
1
10
OUTPUT SWING (VP-P)
10k 20k
1677 G24
Total Harmonic Distortion and
Noise vs Output Amplitude for
Noninverting Gain
TOTAL HARMONIC DISTORTION + NOISE (%)
TOTAL HARMONIC DISTROTION + NOISE (%)
0.01
0.1
1677 G31
Total Harmonic Distortion and
Noise vs Frequency for Inverting
Gain
ZL = 2k/15pF
VO = 20VP-P
AV = –1, –10, – 100
MEASUREMENT BANDWIDTH
= 10Hz TO 80kHz
10
0.0001
10
1677 G23
0.1
125°C
1677 G22
TOTAL HARMONIC DISTROTION + NOISE (%)
30
25°C
Total Harmonic Distortion and
Noise vs Frequency for
Noninverting Gain
–55°C
OUTPUT IMPEDANCE (Ω)
SHORT-CIRCUIT CURRENT (mA)
SINKING
SOURCING
VS = ±15V
–55°C
V– 0
–10 –8 –6 –4 –2 0 2 4 6 8
ISOURCE
ISINK
OUTPUT CURRENT (mA)
10
Closed-Loop Output Impedance
vs Frequency
Output Short-Circuit Current
vs Time
50
8
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
1677 G33
1677 G32
40
Output Voltage Swing
vs Load Current
30
1677 G26
TOTAL HARMONIC DISTORTION + NOISE (%)
0.01% OF
FULL SCALE
SETTLING TIME (µs)
12
Settling Time vs Output Step
(Noninverting)
OUTPUT VOLTAGE SWING (V)
Settling Time vs Output Step
(Inverting)
1
ZL = 2k/15pF
fO = 1kHz
AV = –1, –10, –100
MEASUREMENT BANDWIDTH
= 10Hz TO 22kHz
0.1
AV = –100
0.01
AV = –10
AV = –1
0.001
0.0001
0.3
1
10
OUTPUT SWING (VP-P)
30
1677 G27
LT1677
U
W
U U
APPLICATIO S I FOR ATIO
General
10k
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.
15V
2
–
1
8
7
LT1677
INPUT
3
6
OUTPUT
+
4
–15V
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.
1677 F02
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).
Offset Voltage Adjustment
1k
15V
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
4.7k
2
3
–
+
1
8
LT1677
7 6
OUTPUT
4
–15V
1677 F03
Figure 3. Improved Sensitivity Adjustment
Input = – 0.5V to 3.5V
LT1677 Output
3V
3V
2V
2V
1V
1V
0V
0V
– 0.5V
1577 F01a
– 0.5V
1577 F01b
Figure 1. Voltage Follower with Input Exceeding the Supply Voltage (VS = 3V)
9
LT1677
U
W
U U
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.
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
+
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*
–
100Ω*
3
+
7
LT1677
4
50k*
–15V
6
VOUT
VOUT = 1000VOS
*RESISTORS MUST HAVE LOW
THERMOELECTRIC POTENTIAL
1677 F04
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
1677 F05
Figure 5. Pulsed Operation
Noise Testing
15V
2
LT1677
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.
LT1677
U
W
U U
APPLICATIO S I FOR ATIO
0.1µF
100
90
100k
80
–
2k
*
LT1677
+
+
4.3k
22µF
SCOPE
×1
RIN = 1M
LT1001
4.7µF
–
VOLTAGE GAIN
= 50,000
2.2µF
GAIN (dB)
10Ω
24.3k
60
50
110k
100k
*DEVICE UNDER TEST
NOTE: ALL CAPACITOR VALUES ARE FOR
NONPOLARIZED CAPACITORS ONLY
70
40
30
0.01
0.1µF
0.1
1677 F06a
1
10
FREQUENCY (Hz)
100
1677 F06b
Figure 6b. 0.1Hz to 10Hz Peak-to-Peak
Noise Tester Frequency Response
Figure 6a. 0.1Hz to 10Hz Noise Test Circuit
100k
Current noise is measured in the circuit shown in Figure 7
and calculated by the following formula:
100Ω
1/ 2
2

2
 eno − 130nV • 101 

in = 
1MΩ 101
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
400Ω ≤ RS ≤ 8k at 10Hz
}
500k
+
LT1677
eno
Figure 7
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.
(ii) 400Ω ≤ RS ≤ 50k at 1kHz
–
1677 F07
Resistor noise
dominates
1000
VS = ±15V
TA = 25°C
R
TOTAL NOISE DENSITY (nV/√Hz)
)
( ) (
( )( )
500k
R
SOURCE RESISTANCE = 2R
100
AT 1kHz
AT 10Hz
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
Clearly the LT1677 should not be used in region (iii), where
total system noise is at least six times higher than the
11
LT1677
U
W
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APPLICATIO S I FOR ATIO
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).
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.
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.
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
U
TYPICAL APPLICATIO
Microvolt Comparator with Hysteresis
15V
10M
5%
INPUT
3
+
7
8
2
–
365Ω
1%
LT1677
6
15k
1%
OUTPUT
4
–15V
1677 TA02
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
Q13
×2
IA
Q21
R21
100Ω
R24
100Ω
Q24
Q8
Q9
R9
200Ω
Q1A
RC1A
4.5k
Q3
Q1B
Q12
100µA
IC
Q2A
Q10
PAD
8
Q2B
RC2A
4.5k
RC2B
1k
Q6
Q4
ID
50µA
Q11
Q7
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
R8
200Ω
D2
D3
IB
D1
D4
IA, IB = 200µA VCM > 1.5V ABOVE VEE
0µA VCM < 1.5V ABOVE VEE
R13
100Ω
+IN
–IN
Q5
PAD
1
C10
81pF
Q17
Q15
50µA
Q18
R15
1k
Q19
R19
2k
R14
1k
Q14
Q22
100µA
200µA
R16
1k
Q16
160µA
Q20
R20
2k
+
R25
1k
Q25
Q23
C2
80pF
R2
50Ω
Q32
R30
2k
Q30
Q31
R32
1.5k
R26
100Ω
Q26
R1
500Ω
Q35
Q38
Q34
R3
100Ω
C1
40pF
+
+
RC1B
1k
C3
40pF
Q27
R34
2k
R54
100Ω
C4
20pF
1677 SS
R23B
10k
R23A
10k
+
+
V–
R29
10Ω
Q29
Q28
V+
OUT
LT1677
W
W
SI PLIFIED SCHE ATIC
13
LT1677
U
PACKAGE DESCRIPTIO
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
1
2
3
4
0.255 ± 0.015*
(6.477 ± 0.381)
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
)
0.045 – 0.065
(1.143 – 1.651)
0.065
(1.651)
TYP
0.100
(2.54)
BSC
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)
14
0.130 ± 0.005
(3.302 ± 0.127)
0.125
(3.175) 0.020
MIN
(0.508)
MIN
0.018 ± 0.003
(0.457 ± 0.076)
N8 1098
LT1677
U
PACKAGE DESCRIPTIO
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
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
0.010 – 0.020
× 45°
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
0.053 – 0.069
(1.346 – 1.752)
0°– 8° TYP
0.016 – 0.050
(0.406 – 1.270)
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
2
3
4
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC
SO8 1298
15
LT1677
U
TYPICAL APPLICATIO
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
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
V+
R
LINEAR
TECHNOLOGY
LM334Z
6mA
R8
11Ω
V–
3V
C
LT1431CZ
R
R6
4.99k
+
R7
24.9k
A
R4
14k
C3
220µF
R1
150Ω
GEOSOURCE
MD-105
RL = 847Ω
GEOPHONE
R2
100k
2
–
7
–
LT1677
+
3
C2
0.1µF
Q1
2N3904
12V
R5
243Ω
R10
250Ω
6
VOUT
2.5V ±1V
+
4
R3
16.2k
C4
1000pF
1677 TA03
AV =
R2 + R3||R4
R1 + RL
≅ 107
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT1028
Ultralow Noise Precision Op Amp
Lowest Noise 0.85nV/√Hz
LT1115
Ultralow Noise, Low distortion Audio Op Amp
0.002% THD, Max Noise 1.2nV/√Hz
LT1124/LT1125
Dual/Quad Low Noise, High Speed Precision Op Amps
Similar to LT1007
LT1126/LT1127
Dual/Quad Decompensated Low Noise, High Speed Precision Op Amps
Similar to LT1037
LT1498/LT1499
10MHz, 5V/µs, Dual/Quad Rail-to-Rail Input and Output Op Amps
Precision C-LoadTM Stable
LT1792
Low Noise, Precision JFET Input Op Amp
4.2nV/√Hz, 10fA/√Hz
LT1793
Low Noise, Picoampere Bias Current Op Amp
6nV/√Hz, 1fA/√Hz
LT1884
Dual Rail-to-Rail Output Picoamp Input Precision Op Amp
2.2MHz Bandwidth, 1.2V/µs SR
C-Load is a trademark of Linear Technology Corporation.
16
Linear Technology Corporation
1677i LT/TP 0200 4K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com
 LINEAR TECHNOLOGY CORPORATION 2000