LT1678/LT1679
Dual/Quad Low Noise,
Rail-to-Rail, Precision Op Amps
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FEATURES
DESCRIPTIO
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The LT ®1678/LT1679 are dual/quad rail-to-rail op amps
offering both low noise and precision: 3.9nV/√Hz wideband
noise, 1/f corner frequency of 4Hz and 90nV peak-to-peak
0.1Hz to 10Hz noise are combined with outstanding
precision: 100µV maximum offset voltage, greater than
100dB common mode and power supply rejection and
20MHz gain bandwidth product. The LT1678/LT1679 bring
precision as well as low noise to single supply applications as
low as 3V. The input range exceeds the power supply by
100mV with no phase inversion while the output can swing
to within 170mV of either rail.
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■
■
■
■
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■
Rail-to-Rail Input and Output
100% Tested Low Voltage Noise:
3.9nV/√Hz Typ at 1kHz
5.5nV/√Hz Max at 1kHz
Single Supply Operation from 2.7V to 36V
Offset Voltage: 100µV Max
Low Input Bias Current: 20nA Max
High AVOL: 3V/µV Min, RL = 10k
High CMRR: 100dB Min
High PSRR: 106dB Min
Gain Bandwidth Product: 20MHz
Operating Temperature Range: – 40°C to 85°C
Matching Specifications
No Phase Inversion
8-Lead SO and 14-Lead SO Packages
The LT1678/LT1679 are offered in the SO-8 and SO-14
packages. A full set of matching specifications are also
provided, facilitating their use in matching dependent applications such as a two op amp instrumentation amplifier
design. The LT1678/LT1679 are specified for supply voltages of ±15V, single 5V as well as single 3V. For a single
amplifier with similiar performance, see the LT1677 data
sheet.
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APPLICATIO S
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Strain Gauge Amplifiers
Portable Microphones
Battery-Powered Rail-to-Rail Instrumentation
Low Noise Signal Processing
Microvolt Accuracy Threshold Detection
Infrared Detectors
, LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATIO
Instrumentation Amplifier with Shield Driver
2
0.1Hz to 10Hz Voltage Noise
+
1
1/4
LT1679
1k
VS = ±2.5V
–
RF
3.4k
+
–
15V
5
GUARD
INPUT
30k
8
+
10
–
9
1/4
LT1679
RG
100Ω
6
4
+
1/4
LT1679
–
RG
100Ω
11
–15V
7
OUTPUT
30k
VOLTAGE NOISE (50nV/DIV)
3
GUARD
GAIN = 1000
13
12
–
1/4
LT1679
+
14
0
RF
3.4k
16789 TA01
2
4
6
TIME (sec)
8
10
16789 TA01b
1k
sn16789 16789fs
1
LT1678/LT1679
W W
W
AXI U
U
ABSOLUTE
RATI GS
(Note 1)
Supply Voltage ...................................................... ±18V
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
(Note 4) ............................................. – 40°C to 85°C
Specified Temperature Range
(Note 5) ............................................. – 40°C to 85°C
U
U
W
PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
TOP VIEW
OUT A 1
–IN A 2
+IN A 3
8 V
LT1678CS8
LT1678IS8
+
7 OUT B
A
B
V– 4
6 –IN B
S8 PACKAGE
8-LEAD PLASTIC SO
S8 PART MARKING
TJMAX = 150°C, θJA = 190°C/ W
1678
1678I
14 OUT D
OUT A 1
–IN A 2
A
D
LT1679CS
LT1679IS
13 –IN D
12 +IN D
+IN A 3
V+ 4
+IN B 5
5 +IN B
ORDER PART
NUMBER
TOP VIEW
11 V –
B
C
10 +IN C
–IN B 6
9
–IN C
OUT B 7
8
OUT C
S PACKAGE
14-LEAD PLASTIC SO
TJMAX = 150°C, θJA = 160°C/ W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VS = 3V, VCM = VO = 1.7V; VS = 5V, VCM = VO = 2.5V unless
otherwise noted.
SYMBOL
PARAMETER
CONDITIONS (Note 6)
VOS
Input Offset Voltage
(Note 11)
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
∆VOS
∆Temp
IB
TYP
MAX
UNITS
●
●
35
55
75
100
270
350
µV
µV
µV
VS =5V, VCM = VS + 0.1V
VS =5V, VCM = VS – 0.3V, 0°C ≤ TA ≤ 70°C
VS =5V, VCM = VS – 0.3V, – 40°C ≤ TA ≤ 85°C
●
●
150
180
200
550
750
1000
µV
µV
µV
VS =5V, VCM = – 0.1V
VS =5V, VCM = 0V, 0°C ≤ TA ≤ 70°C
VS =5V, VCM = 0V, – 40°C ≤ TA ≤ 85°C
●
●
1.5
1.8
2.0
30
45
50
mV
mV
mV
●
0.40
3
µV/°C
●
●
±2
±3
±7
±20
±35
±50
nA
nA
nA
0.19
0.19
0.25
0.40
0.60
0.75
µA
µA
µA
Average Input Offset Drift (Note 10)
Input Bias Current
(Note 11)
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
MIN
VS = 5V, VCM = VS + 0.1V
●
VS = 5V, VCM = VS – 0.3V, 0°C ≤ TA ≤ 70°C
VS = 5V, VCM = VS – 0.3V, – 40°C ≤ TA ≤ 85°C ●
VS = 5V, VCM = – 0.1V
VS = 5V, VCM = 0V, 0°C ≤ TA ≤ 70°C
VS = 5V, VCM = 0V, – 40°C ≤ TA ≤ 85°C
●
●
–5
–8.4
–10
– 0.41
– 0.45
– 0.47
µA
µA
µA
sn16789 16789fs
2
LT1678/LT1679
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VS = 3V, VCM = VO = 1.7V; VS = 5V, VCM = VO = 2.5V unless
otherwise noted.
SYMBOL
PARAMETER
CONDITIONS (Note 6)
IOS
Input Offset Current
(Note 11)
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
TYP
MAX
●
●
4
5
8
25
35
55
nA
nA
nA
VS = 5V, VCM = VS + 0.1V
VS = 5V, VCM = VS – 0.3V, 0°C ≤ TA ≤ 70°C
●
VS = 5V, VCM = VS – 0.3V, – 40°C ≤ TA ≤ 85°C ●
6
10
15
30
40
65
nA
nA
nA
0.1
0.1
0.15
1.6
2.0
2.4
µA
µA
µA
VS = 5V, VCM = – 0.1V
VS = 5V, VCM = 0V, 0°C ≤ TA ≤ 70°C
VS = 5V, VCM = 0V, – 40°C ≤ TA ≤ 85°C
en
0.1Hz to 10Hz (Note 7)
VCM = VS
VCM = 0V
Input Noise Voltage Density (Note 8)
fO = 10Hz
VCM = VS, fO = 10Hz
VCM = 0V, fO = 10Hz
4.4
6.6
19
fO = 1kHz
VCM = VS, fO = 1kHz
VCM = 0V, fO = 1kHz
3.9
5.3
9
fO = 10Hz
fO = 1kHz
1.2
0.3
Input Noise Current Density
VCM
Input Voltage Range
RIN
Input Resistance
CIN
Input Capacitance
CMRR
Common Mode Rejection Ratio
AVOL
VOL
●
●
Input Noise Voltage
in
PSRR
MIN
90
180
1600
●
Power Supply Rejection Ratio
Large-Signal Voltage Gain
Output Voltage Swing Low (Note 11)
UNITS
– 0.1
0
Common Mode
nVP-P
nVP-P
nVP-P
nV/√Hz
nV/√Hz
nV/√Hz
5.5
nV/√Hz
nV/√Hz
nV/√Hz
pA/√Hz
pA/√Hz
VS + 0.1V
VS – 0.3V
2
V
V
GΩ
4.2
pF
●
98
92
120
120
dB
dB
●
100
98
125
120
dB
dB
●
0.6
0.3
3
2
V/µV
V/µV
VS = 3V, RL = 2k, VO = 2.2V to 0.7V
0°C ≤ TA ≤ 70°C
–40°C ≤ TA ≤ 85°C
●
●
0.5
0.4
0.4
3
0.9
0.8
V/µV
V/µV
V/µV
VS = 3V, RL = 600Ω, VO = 2.2V to 0.7V
0°C ≤ TA ≤ 70°C
–40°C ≤ TA ≤ 85°C
●
●
0.20
0.15
0.10
0.43
0.40
0.35
V/µV
V/µV
V/µV
VS = 5V, RL = 10k, VO = 4.5V to 0.7V
O°C < TA < 70°C
–40 < TA < 85°C
●
●
1
0.6
0.3
3.8
2
2
V/µV
V/µV
V/µV
VS = 5V, RL = 2k, VO = 4.2V to 0.7V
0°C ≤ TA ≤ 70°C
–40°C ≤ TA ≤ 85°C
●
●
0.7
0.6
0.5
3.5
3.2
3.0
V/µV
V/µV
V/µV
VS = 5V, RL = 600Ω, VO = 4.2V to 0.7V
0°C ≤ TA ≤ 70°C
–40°C ≤ TA ≤ 85°C
●
●
0.6
0.5
0.4
3.0
2.8
2.5
V/µV
V/µV
V/µV
Above GND
ISINK = 0.1mA
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
●
●
VS = 5V, VCM = 1.9V to 3.9V
VS = 5V, VCM = 1.9V to 3.9V
VS = 2.7V to 36V, VCM = VO = 1.7V
VS = 3.1V to 36V, VCM = VO = 1.7V
VS = 3V, RL = 10k, VO = 2.5V to 0.7V
80
125
130
170
200
250
mV
mV
mV
sn16789 16789fs
3
LT1678/LT1679
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VS = 3V, VCM = VO = 1.7V; VS = 5V, VCM = VO = 2.5V unless
otherwise noted.
SYMBOL
PARAMETER
CONDITIONS (Note 6)
VOL
Output Voltage Swing Low (Note 11)
Above GND
ISINK = 2.5mA
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
VOH
ISC
Output Voltage Swing High (Note 11)
Output Short-Circuit Current (Note 3)
MIN
TYP
MAX
UNITS
●
●
170
195
205
250
320
350
mV
mV
mV
Above GND
ISINK = 10mA
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
●
●
370
440
465
600
720
770
mV
mV
mV
Below VS
ISOURCE = 0.1mA
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
●
●
75
85
93
150
200
250
mV
mV
mV
Below VS
ISOURCE = 2.5mA
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
●
●
110
195
205
250
350
375
mV
mV
mV
Below VS
ISOURCE = 10mA
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
●
●
170
200
230
400
500
550
mV
mV
mV
VS = 3V
●
15
13
22
19
mA
mA
●
18
14
29
25
mA
mA
AV = – 1, RL = 10k
RL = 10k, 0°C ≤ TA ≤ 70°C
RL = 10k, – 40°C ≤ TA ≤ 85°C
●
●
4
3.5
3
6
5.8
5.5
V/µs
V/µs
V/µs
fO = 100kHz
fO = 100kHz
●
13
12.5
20
19
MHz
MHz
VS = 5V
SR
GBW
Slew Rate (Note 13)
Gain Bandwidth Product (Note 11)
tS
Settling Time
2V Step 0.1%, AV = +1
2V Step 0.01%, AV = +1
1.4
2.4
µs
µs
RO
Open-Loop Output Resistance
Closed-Loop Output Resistance
IOUT = 0
AV = 100, f = 10kHz
100
1
Ω
Ω
IS
Supply Current per Amplifier (Note 12)
∆VOS
∆IB+
∆CMRR
∆PSRR
Offset Voltage Match
(Notes 11, 15)
Noninverting Bias Current Match
(Notes 11, 15)
●
2
2.5
3.4
3.8
mA
mA
0°C ≤ TA ≤ 70°C
–40°C ≤ TA ≤ 85°C
●
●
35
55
75
150
400
525
µV
µV
µV
0°C ≤ TA ≤ 70°C
–40°C ≤ TA ≤ 85°C
●
●
±2
±3
±7
±30
±55
±75
nA
nA
nA
Common Mode Rejection Match
(Notes 11, 14, 15)
VS = 5V, VCM = 1.9V to 3.9V
Power Supply Rejection Match
(Notes 11, 14, 15)
VS = 2.7V to 36V, VCM = VO = 1.7V
VS = 3.1V to 36V, VCM = VO = 1.7V
●
94
88
110
110
dB
dB
●
96
94
120
120
dB
dB
sn16789 16789fs
4
LT1678/LT1679
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VS = ±15V, VCM = VO = 0V unless otherwise noted.
SYMBOL
PARAMETER
VOS
Input Offset Voltage
CONDITIONS (Note 6)
TYP
MAX
UNITS
●
●
20
30
45
150
350
420
µV
µV
µV
●
0.40
3
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
●
●
±2
±3
±7
±20
±35
±50
nA
nA
nA
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
●
●
3
5
8
25
35
55
nA
nA
nA
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
∆VOS
∆Temp
Average Input Offset Drift (Note 10)
IB
Input Bias Current
IOS
en
Input Offset Current
Input Noise Voltage
0.1Hz to 10Hz (Note 7)
VCM = 15V
VCM = –15V
90
180
1600
Input Noise Voltage Density
fO = 10Hz
VCM = 15V, fO = 10Hz
VCM = –15V, fO = 10Hz
4.4
6.6
19
fO = 1kHz
VCM = 15V, fO = 1kHz
VCM = –15V, fO = 1kHz
3.9
5.3
9
fO = 10Hz
fO = 1kHz
1.2
0.3
in
Input Noise Current Density
VCM
Input Voltage Range (Note 16)
RIN
Input Resistance
CIN
Input Capacitance
CMRR
Common Mode Rejection Ratio
PSRR
AVOL
MIN
Power Supply Rejection Ratio
Large-Signal Voltage Gain
●
– 13.3
Common Mode
VCM = –13.3V to 14V
µV/°C
nVP-P
nVP-P
nVP-P
nV/√Hz
nV/√Hz
nV/√Hz
5.5
nV/√Hz
nV/√Hz
nV/√Hz
pA/√Hz
pA/√Hz
14
V
2
GΩ
4.2
pF
●
100
96
130
124
dB
dB
●
106
100
130
125
dB
dB
RL = 10k, VO = ±14V
0°C ≤ TA ≤ 70°C
–40°C ≤ TA ≤ 85°C
●
●
3
2
1
7
6
4
V/µV
V/µV
V/µV
RL = 2k, VO = ±13.5V
0°C ≤ TA ≤ 70°C
–40°C ≤ TA ≤ 85°C
●
●
0.8
0.5
0.4
1.7
1.4
1.1
V/µV
V/µV
V/µV
VS = ±1.7V to ±18V
sn16789 16789fs
5
LT1678/LT1679
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VS = ±15V, VCM = VO = 0V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS (Note 6)
VOL
Output Voltage Swing Low
Above – VS
ISINK = 0.1mA
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
VOH
Output Voltage Swing High
ISC
Output Short-Circuit Current (Note 3)
SR
Slew Rate
GBW
Gain Bandwidth Product
TYP
MAX
UNITS
●
●
110
125
130
200
230
260
mV
mV
mV
Above – VS
ISINK = 2.5mA
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
●
●
170
195
205
280
350
380
mV
mV
mV
Above – VS
ISINK = 10mA
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
●
●
370
440
450
600
700
750
mV
mV
mV
Below +VS
ISOURCE = 0.1mA
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
●
●
80
90
100
150
200
250
mV
mV
mV
Below +VS
ISOURCE = 2.5mA
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
●
●
110
120
120
200
300
350
mV
mV
mV
Below +VS
ISOURCE = 10mA
0°C ≤ TA ≤ 70°C
– 40°C ≤ TA ≤ 85°C
●
●
200
250
250
450
500
550
mV
mV
mV
●
20
15
35
28
mA
mA
RL = 10k (Note 9)
RL = 10k (Note 9) 0°C ≤ TA ≤ 70°C
RL = 10k (Note 9) – 40°C ≤ TA ≤ 85°C
●
●
4
3.5
3
6
5.8
5.5
V/µs
V/µs
V/µs
fO = 100kHz
fO = 100kHz
●
13
12.5
20
19
MHz
MHz
THD
Total Harmonic Distortion
RL = 2k, AV = 1, fO = 1kHz, VO = 20VP-P
tS
Settling Time
RO
Open-Loop Output Resistance
Closed-Loop Output Resistance
IS
Supply Current per Amplifier
∆IB+
∆CMRR
∆PSRR
0.00025
%
10V Step 0.1%, AV = +1
10V Step 0.01%, AV = +1
2.7
3.9
µs
µs
IOUT = 0
AV = 100, f = 10kHz
100
1
Ω
Ω
2.5
3
●
Channel Separation
∆VOS
MIN
Offset Voltage Match
(Note 15)
Noninverting Bias Current Match
(Note 15)
f = 10Hz, VO = ±10V, RL = 10k
3.5
4.5
132
mA
mA
dB
0°C ≤ TA ≤ 70°C
–40°C ≤ TA ≤ 85°C
●
●
5
30
45
225
525
630
µV
µV
µV
0°C ≤ TA ≤ 70°C
–40°C ≤ TA ≤ 85°C
●
●
±2
±3
±7
±30
±55
±75
nA
nA
nA
Common Mode Rejection Match
(Notes 14, 15)
VCM = –13.3V to 14V
Power Supply Rejection Match
(Notes 14, 15)
VS = ±1.7V to ±18V
●
96
92
120
115
dB
dB
●
100
96
123
120
dB
dB
sn16789 16789fs
6
LT1678/LT1679
ELECTRICAL CHARACTERISTICS
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 LT1678C/LT1679C and LT1678I/LT1679I are guaranteed
functional over the Operating Temperature Range of – 40°C to 85°C.
Note 5: The LT1678C/LT1679C are guaranteed to meet specified
performance from 0°C to 70°C. The LT1678C/LT1679C are 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 LT1678I/
LT1679I are guaranteed to meet specified performance from – 40°C to
85°C.
Note 6: Typical parameters are defined as the 60% yield of parameter
distributions of individual amplifier; i.e., out of 100 LT1678/LT1679s,
typically 60 op amps will be better than the indicated specification.
Note 7: See the test circuit and frequency response curve for 0.1Hz to10Hz
tester in the Applications Information section.
Note 8: Noise is 100% tested at ±15V supplies.
Note 9: Slew rate is measured in AV = – 1; input signal is ±10V, output
measured at ±5V.
Note 10: This parameter is not 100% tested.
Note 11: VS = 5V limits are guaranteed by correlation to VS = 3V and
VS = ±15V tests.
Note 12: VS = 3V limits are guaranteed by correlation to VS = 5V and
VS = ±15V tests.
Note 13: Guaranteed by correlation to slew rate at VS = ±15V and GBW at
VS = 3V and VS = ±15V tests.
Note 14: ∆CMRR and ∆PSRR are defined as follows:
1. CMRR and PSRR are measured in µV/V on the individual amplifiers.
2. The difference is calculated between the matching sides in µV/V.
3. The result is converted to dB.
Note 15: Matching parameters are the difference between amplifiers A and
B on the LT1678 and between amplifiers A and D and B and C in the
LT1679.
Note 16: Input range guaranteed by the common mode rejection ratio test.
U W
TYPICAL PERFOR A CE CHARACTERISTICS
VS = 5V, 0V
VCM = 14.5V
VCM = 0V
10
100
FREQUENCY (Hz)
1000
16789 G01
VOLTAGE NOISE (50nV/DIV)
10
1
VS = 5V, 0V
VOLTAGE NOISE (50nV/DIV)
NOISE VOLTAGE (nV/√Hz)
VS = ±15V
TA = 25°C
1
0.1
0.01Hz to 1Hz Voltage Noise
0.1Hz to 10Hz Voltage Noise
Voltage Noise vs Frequency
100
0
2
4
6
TIME (sec)
8
10
16789 G02
0
20
40
60
TIME (sec)
80
100
16789 G03
sn16789 16789fs
7
LT1678/LT1679
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Voltage Noise vs Temperature
Input Bias Current vs Temperature
Current Noise vs Frequency
10
VS = ±15V
VCM = 0V
NOISE VOLTAGE (pA/√Hz)
5
10Hz
4
1kHz
3
2
16
VS = ±15V
TA = 25°C
14
VCM = 0V
1
VCM = 14.5V
8
6
4
2
0
–4
50
25
0
75
TEMPERATURE (°C)
–25
100
0.1
0.01
125
0.1
1
FREQUENCY (kHz)
Input Bias Current Over the
Common Mode Range
INPUT BIAS CURRENT (nA)
800
600
400
VCM = 14.7V
CURRENT INTO DUT
0
–50
–25
25
0
50
75
TEMPERATURE (°C)
100
125
500
4
400
3
500
300
VCM = –13.5V
100
VCM = 14.5V
INPUT BIAS CURRENT
–100
VCM = 14.1V
–300
100
0
0
–1
–100
–2
–200
–700
–4
VCM = –15.2V
0
8
4
–16 –12 –8 –4
12
COMMON MODE INPUT VOLTAGE (V)
16
–5
–1.0
6
4
2
VS = 5V, 0V
VCM = 0V
100
20
15
0
3
4
TIME (min)
16789 G10
0
–100
10
–200
5
2
–500
200
VOLTAGE OFFSET (µV)
PERCENT OF UNITS (%)
8
–400
VOS vs Temperature of
Representive Units
VS = 5V, 0V
TA = –40°C TO 85°C
25 111 PARTS (2 LOTS)
SO PACKAGE
1.0
–300
16789 G09
30
VS = ±15V
TA = 25°C
1
2.0 –0.8 –0.4 V + 0.4
–
VCM – V (V)
VCM – V+ (V)
V–
Distribution of Input Offset
Voltage Drift (SO-8)
10
0
VS = ±1.5V TO ±15V
TA = 25°C
5 TYPICAL PARTS
16789 G08
Warm-Up Drift vs Time
200
1
–3
–900
300
VOS IS REFERRED TO
VCM = 0V
2
–500
16789 G07
0
5
OFFSET VOLTAGE (µV)
1000
200
VS = ±15V
TA = 25°C
700
125
Offset Voltage Shift vs
Common Mode
OFFSET VOLTAGE (mV)
VCM = –14V
CURRENT OUT OF DUT
1200
100
16789 G06
900
VS = ±15V
50
25
75
0
TEMPERATURE (°C)
16789 G05
Input Bias Current vs Temperature
1400
–6
–50 –25
10
16789 G04
INPUT BIAS CURRENT (nA)
10
–2
1
–50
CHANGE IN OFFSET VOLTAGE (µV)
VS = ±15V
VCM = 0V
12
INPUT BIAS CURRENT (nA)
RMS VOLTAGE NOISE DENSITY (nV/√Hz)
6
–3.0
1.0 2.0
3.0
–2.0 –1.0 0
INPUT OFFSET VOLTAGE DRIFT (µV/°C)
16789 G11
–300
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
16789 G12
sn16789 16789fs
8
LT1678/LT1679
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Common Mode Range vs
Temperature
500
400
3
300
2
200
25°C
–55°C
1
100
–55°C
125°C
0
0
25°C
–1
–100
VOS IS REFERRED TO
VCM = 0V
–2
–3
–200
–300
125°C
–400
–4
–5
–1.0
–500
V– 1.0 2.0 –0.8 –0.4 V – 0.4
VCM – VS+ (V)
VCM – VS– (V)
3.5
3.0
TA = 125°C
2.5
TA = 25°C
2.0
TA = –55°C
1.5
1.0
0
±5
±10
±15
SUPPLY VOLTAGE (V)
COMMON MODE REJECTION RATIO (dB)
4
160
4.0
SUPPLY CURRENT PER AMPLIFIER (mA)
VS = ±2.5V TO ±15V
OFFSET VOLTAGE (µV)
OFFSET VOLTAGE (mV)
5
Common Mode Rejection Ratio
vs Frequency
Supply Current vs Supply Voltage
140
VS = ±15V
TA = 25°C
VCM = 0V
120
100
80
60
40
20
0
10k
±20
100k
1M
FREQUENCY (Hz)
10M
16789 G14
16789 G15
16789 G09
Power Supply Rejection Ratio
vs Frequency
VS = ±15V
TA = 25°C
120
100
NEGATIVE SUPPLY
80
60
POSITIVE SUPPLY
40
20
0
0.001
VS = ±15V
RL = 2k TO 10k
50 AV = 1
TA = 25°C
RL = 10k
RL = 2k
1
TA = 25°C
RL TO GND
VCM = VO = VS/2
0.1
0.01
0.1
1
10
FREQUENCY (kHz)
100
0
1000
10
20
SUPPLY VOLTAGE (V)
Phase Margin, Gain Bandwidth
Product and Slew Rate vs
Temperature
PHASE MARGIN (DEG)
20
SLEW RATE (V/µs)
8
15
VS = ±15V
CL = 15pF
AV = –1
RF = RG = 1k
60
30
50
GAIN BANDWIDTH PRODUCT
25
10
6
+SR
–SR
4
–55 –35 –15
5 25 45 65 85 105 125
TEMPERATURE (°C)
GAIN BANDWIDTH PRODUCT, fO = 100kHz (MHz)
40
PHASE MARGIN
30
RISING EDGE
20
FALLING EDGE
10
0
30
10
100
CAPACITIVE LOAD (pF)
1000
16789 G18
Small Signal
Transient Response
Large Signal
Transient Response
90
80
40
16789 G17
16789 G16
70
% Overshoot vs Capacitive Load
60
OVERSHOOT (%)
140
Voltage Gain vs Supply Voltage
10
OPEN LOOP VOLTAGE GAIN (V/µV)
POWER SUPPLY REJECTION RATIO (dB)
160
50mV
10V
0V
–10V
–50mV
AVCL = –1
VS = ±15V
AVCL = 1
VS = ±15V
CL = 15pF
5µs/DIV
16789 G20
0.5µs/DIV
16789 G21
16789 G19
sn16789 16789fs
9
LT1678/LT1679
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Settling Time vs Output
Step (Inverting)
Settling Time vs Output
Step (Noninverting)
5k
VIN
–
VOUT
4
3
0.01% OF
FULL SCALE
0.01% OF
FULL SCALE
2
1
0.1% OF
FULL SCALE
0.1% OF
FULL SCALE
0
–10 –8 –6
–4 –2 0 2 4
OUTPUT STEP (V)
6
8
VIN
VOUT
+
RL = 1k
4
0.01% OF
FULL SCALE
3
0.01% OF
FULL SCALE
2
0
–10 –8 –6
10
–4 –2 0 2 4
OUTPUT STEP (V)
Gain, Phase Shift vs Frequency
20
40
TA = –55°C
10
TA = 125°C
0
–10
20
GAIN
0
TA = 25°C
0.1
40
20
20
TA = 25°C
TA = 25°C
GAIN
AV = 1
0.01
0.001
10k
1k
FREQUENCY (Hz)
100k
1M
16789 G28
–20
100
1
10
FREQUENCY (MHz)
0
–0.1
0
VS = ±15V
–20
100
1
10
FREQUENCY (MHz)
–VS
TA = –55°C
TA = 125°C
TA = 25°C
–0.2
–0.3
0.8
0.7
TA = 125°C
0.6
0.5
TA = 25°C
0.4
0.3
0.2
TA = –55°C
0.1
TA = –55°C
0.1
+VS
0
–10 –8 –6 –4 –2 0 2 4 6
OUTPUT CURRENT (mA)
16789 G26
ZL = 2k/15pF
VS = ±15V
VO = 20VP-P
AV = 1, 10, 100
MEASUREMENT BANDWIDTH
0.01 = 10Hz TO 80kHz
AV = 100
0.001
AV = 10
AV = 1
100
1k
FREQUENCY (Hz)
10k
10
Total Harmonic Distortion and
Noise vs Frequency for
Noninverting Gain
0.1
0.0001
20
8
16789 G27
TOTAL HARMONIC DISTORTION + NOISE (%)
AV = 100
100
40
TA = 125°C
10
–10
TOTAL HARMONIC DISTORTION + NOISE (%)
OUTPUT IMPEDANCE (Ω)
10
10
TA = –55°C
0.1
Total Harmonic Distortion and
Noise vs Frequency for
Noninverting Gain
VS = ±15V
0.1
0
Output Voltage Swing vs
Load Current
PHASE
TA = –55°C
Closed-Loop Output
Impedance vs Frequency
1
20
GAIN
16789 G24
60
16789 G25
100
–10
10
30
0
–20
100
1
10
FREQUENCY (MHz)
VOLTAGE GAIN (dB)
VOLTAGE GAIN (dB)
60
TA = 125°C
40
TA = 125°C
10
PHASE SHIFT (DEG)
TA = –55°C
TA = 25°C
TA = 25°C
TA = 125°C 60
0
100
VS = ±15V
VCM = –14V
80
CL = 10pF
50
PHASE SHIFT (DEG)
PHASE
30
20
Gain, Phase Shift vs Frequency
100
VS = ±15V
VCM = 14.7V
80
CL = 10pF
40
8
30
16789 G23
16789 G22
50
6
TA = –55°C
TA = 25°C
0.1% OF
FULL SCALE
0.1% OF
1 FULL SCALE
PHASE
40
–
2k
100
VS = ±15V
VCM = 0V
CL = 10pF 80
PHASE SHIFT (DEG)
SETTLING TIME (µs)
+
2k
VS = ±15V
AV = 1
5 TA = 25°C
5k
Gain, Phase Shift vs Frequency
50
OUTPUT VOLTAGE SWING (V)
VS = ±15V
AV = –1
TA = 25°C
SETTLING TIME (µs)
5
6
VOLTAGE GAIN (dB)
6
50k
16789 G29
0.1
ZL = 2k/15pF
VS = ±15V
VO = 20VP-P
AV = –1, –10, –100
MEASUREMENT BANDWIDTH
0.01 = 10Hz TO 80kHz
AV = –100
0.001
AV = –10
AV = –1
0.0001
20
100
1k
FREQUENCY (Hz)
10k
50k
16789 G30
sn16789 16789fs
10
LT1678/LT1679
U
W
U U
APPLICATIO S I FOR ATIO
Rail-to-Rail Operation
To take full advantage of an input range that can exceed
the supply, the LT1678/LT1679 are designed to eliminate
phase reversal. Referring to the photographs shown in
Figure 1, the LT1678/LT1679 are operating in the follower mode (AV = +1) at a single 3V supply. The output
of the LT1678/LT1679 clips cleanly and recovers with no
phase reversal. This has the benefit of preventing lock-up
in servo systems and minimizing distortion components.
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,
creating additional phase shift and reducing the phase
margin. A small capacitor (20pF to 50pF) in parallel with RF
will eliminate this problem.
RF
Input = –0.5V to 3.5V
–
6V/µs
3
INPUT VOLTAGE (V)
OUTPUT
+
2
LT1678
16789 F02
Figure 2. Pulsed Operation
1
Noise Testing
0
–0.5
50µs/DIV
16789 F01a
LT1678 Output
OUTPUT VOLTAGE (V)
3
2
The 0.1Hz to 10Hz peak-to-peak noise of the LT1678/
LT1679 are measured in the test circuit shown (Figure 3).
The frequency response of this noise tester (Figure 4)
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 90nV peak-to-peak noise performance of the LT1678/LT1679 requires special test precautions:
1
0
–0.5
50µs/DIV
16789 F01b
Figure 1. Voltage Follower with Input Exceeding the Supply
Voltage (VS = 3V)
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 2).
During the fast feedthrough-like portion of the output, the
input protection diodes effectively short the output to the
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.
sn16789 16789fs
11
LT1678/LT1679
U
W
U U
APPLICATIO S I FOR ATIO
100
0.1µF
90
100k
GAIN (dB)
10Ω
80
–
2k
*
LT1678
+
+
4.3k
22µF
SCOPE
×1
RIN = 1M
LT1001
4.7µF
–
VOLTAGE GAIN
= 50,000
2.2µF
24.3k
60
50
110k
40
100k
*DEVICE UNDER TEST
NOTE: ALL CAPACITOR VALUES ARE FOR
NONPOLARIZED CAPACITORS ONLY
70
30
0.01
0.1µF
16789 F03
0.1
1
10
FREQUENCY (Hz)
100
16789 F04
Figure 4. 0.1Hz to 10Hz Peak-to-Peak
Noise Tester Frequency Response
Figure 3. 0.1Hz to 10Hz Noise Test Circuit
3. Sudden motion in the vicinity of the device can also
“feedthrough” to increase the observed noise.
Total Noise = [(op amp voltage noise)2 + (resistor noise)2
+ (current noise RS)2]1/2
Current noise is measured in the circuit shown in Figure 5
and calculated by the following formula:
Three regions can be identified as a function of source
resistance:
1/ 2
(i) RS ≤ 400Ω. Voltage noise dominates
(ii) 400Ω ≤ RS ≤ 50k at 1kHz Resistor Noise
400Ω ≤ RS ≤ 8k at 10Hz Dominates
2⎤
⎡
2
⎢ eno − 130nV • 101 ⎥
⎦
in = ⎣
1MΩ 101
)
( ) (
( )( )
(iii) RS > 50k at 1kHz Current Noise
RS > 8k at 10Hz Dominates
100k
100Ω
500k
–
500k
+
LT1678
eno
16789 F05
Figure 5.
Clearly the LT1678/LT1679 should not be used in region
(iii), where total system noise is at least six times higher
than the voltage noise of the op amp, i.e., the low voltage
noise specification is completely wasted. In this region the
LT1113 or LT1169 are better choices.
1000
VS = ±15V
TA = 25°C
The LT1678/LT1679 achieve their low noise, in part, by
operating the input stage at 100µA 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
LT1678/LT1679’s current noise will be relatively high. At
low frequencies, the low 1/f current noise corner frequency (≈ 200Hz) 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 6) where:
TOTAL NOISE DENSITY (nV/√Hz)
R
R
SOURCE RESISTANCE = 2R
100
AT 1kHz
AT 10Hz
10
RESISTOR
NOISE ONLY
1
0.1
1
10
SOURCE RESISTANCE (kΩ)
100
16789 F06
Figure 6. Total Noise vs Source Resistance
sn16789 16789fs
12
LT1678/LT1679
U
W
U U
APPLICATIO S I FOR ATIO
Rail-to-Rail Input
Rail-to-Rail Output
The input common mode range for the LT1678/LT1679
can exceed the supplies by at least 100mV. As the
common mode voltage approaches the positive rail (+VS
– 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 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).
The rail-to-rail output swing is achieved by using transistor collectors (Q28, Q29 referring to the Simplified Schematic) instead of customary class A-B emitter followers for
the output stage. The output NPN transistor (Q29) sinks the
current necessary to move the output in the negative direction. The change in Q29’s base emitter voltage is reflected
directly to the gain node (collectors of Q20 and Q16). For
large sinking currents, the delta VBE of Q29 can dominate
the gain. Figure 7 shows the change in input voltage for a
change in output voltage for different load resistors connected between the supplies. The gain is much higher for
output voltages above ground (Q28 sources current) since
the change in base emitter voltage of Q28 is attenuated by
the gain in the PNP portion of the output stage. Therefore,
for positive output swings (output sourcing current) there
is hardly any change in input voltage for any load resistance.
Highest gain and best linearity are achieved when the output
is sourcing current, which is the case in single supply operation when the load is ground referenced. Figure 8 shows
gains for both sinking and sourcing load currents for a
worst-case load of 600Ω.
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 Shift vs
Common Mode shows where the knees occur by displaying the change in offset voltage. The change-over points
are temperature dependent; see the graph Common Mode
Range vs Temperature.
RL = 600Ω
RL = 1k
INPUT VOLTAGE
(50µV/DIV)
RL TO 0V
RL = 10k
INPUT VOLTAGE
(10µV/DIV)
RL TO 5V
TA = 25°C
VS = ±15V
RL CONNECTED TO 0V
MEASURED ON
TEKTRONIX 577
CURVE TRACER
–15 –10 –5
0
5 10 15
OUTPUT VOLTAGE (V)
0
16789 F07
Figure 7. Voltage Gain Split Supply
VOLTAGE GAIN SINGLE SUPPLY
VS = 5V
RL = 600Ω
MEASURED ON TEKTRONIX 577
CURVE TRACER
1
2
3
OUTPUT VOLTAGE (V)
4
5
16789 F08
Figure 8. Voltage Gain Single Supply
sn16789 16789fs
13
Q13
×2
IA
Q21
R21
100Ω
R24
100Ω
Q24
Q8
R8
200Ω
Q9
D2
D3
IB
D1
D4
R9
200Ω
Q1A
Q3
Q1B
Q12
100µA
IC
C10
81pF
Q2A
Q10
Q2B
RC2
6k
Q6
Q4
ID
50µA
Q11
Q7
IA, IB = 0µA VCM > 1.5V ABOVE –VS IC = 200µA VCM < 0.7V BELOW +VS ID = 100µA VCM < 0.7V BELOW +VS
200µA VCM < 1.5V ABOVE –VS
50µA VCM > 0.7V BELOW +VS
0µA VCM > 0.7V BELOW +VS
R13
100Ω
+IN
–IN
Q5
RC1
6k
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 Q38
100Ω
Q26
R1
500Ω
C1
40pF
R3
100Ω
+
Q35
Q34
C3
40pF
Q27
R34
2k
R54
100Ω
16789 SS
R23B
10k
R29
10Ω
Q29
Q28
–VS
C4
20pF
R23A
10k
+
+
14
+
+VS
OUT
LT1678/LT1679
W
W
SI PLIFIED SCHE ATIC
sn16789 16789fs
LT1678/LT1679
U
PACKAGE DESCRIPTIO
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
.189 – .197
(4.801 – 5.004)
NOTE 3
.045 ±.005
.050 BSC
7
8
.245
MIN
5
6
.160 ±.005
.150 – .157
(3.810 – 3.988)
NOTE 3
.228 – .244
(5.791 – 6.197)
.030 ±.005
TYP
1
RECOMMENDED SOLDER PAD LAYOUT
.010 – .020
× 45°
(0.254 – 0.508)
3
2
4
.053 – .069
(1.346 – 1.752)
.008 – .010
(0.203 – 0.254)
.004 – .010
(0.101 – 0.254)
0°– 8° TYP
.016 – .050
(0.406 – 1.270)
.050
(1.270)
BSC
.014 – .019
(0.355 – 0.483)
TYP
NOTE:
1. DIMENSIONS IN
INCHES
(MILLIMETERS)
2. DRAWING NOT TO SCALE
3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
SO8 0303
S Package
14-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
.337 – .344
(8.560 – 8.738)
NOTE 3
.045 ±.005
.050 BSC
14
N
12
11
10
9
8
N
.245
MIN
.160 ±.005
.150 – .157
(3.810 – 3.988)
NOTE 3
.228 – .244
(5.791 – 6.197)
1
.030 ±.005
TYP
13
2
3
N/2
N/2
RECOMMENDED SOLDER PAD LAYOUT
1
.010 – .020
× 45°
(0.254 – 0.508)
.008 – .010
(0.203 – 0.254)
2
3
4
5
6
.053 – .069
(1.346 – 1.752)
.004 – .010
(0.101 – 0.254)
0° – 8° TYP
.016 – .050
(0.406 – 1.270)
NOTE:
1. DIMENSIONS IN
.014 – .019
(0.355 – 0.483)
TYP
7
.050
(1.270)
BSC
INCHES
(MILLIMETERS)
2. DRAWING NOT TO SCALE
3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
S14 0502
sn16789 16789fs
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.
15
LT1678/LT1679
U
TYPICAL APPLICATIO
Bridge Reversal Eliminates 1/f Noise and Offset Drift of a Low Noise, Non-autozeroed, Bipolar Amplifier.
Circuit Gives 14nV Noise Level or 19 Effective Bits Over a 10mV Span
VREF
3
4
VREF
7V
φ1
5,6,7,8
LT1461-5
2
10µF
0.1µF
5V
+
100k
10Ω
1
1/2 LT1678
–
0.047µF
350Ω
350Ω
350Ω
350Ω
VREF
100k
3
4
5,6,7,8
2
100Ω
IN+
1µF
100Ω
0.1%
–
REF+
1k
0.1%
1k
0.1%
LTC2440
100Ω
IN–
1µF
0.047µF
REF –
10Ω
1/2 LT1678
+
2X
SILICONIX
Si9801
φ2
φ1
φ2
1
≈2s
16789 TA02
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT1028/LT1128
Ultralow Noise Precision Op Amps
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
LT1226
Low Noise, Very High Speed Op Amp
1GHz, 2.6nV/√Hz, Gain of 25 Stable
LT1498/LT1499
10MHz, 5V/µs, Dual/Quad Rail-to-Rail Input and Output Op Amps
Precision C-LoadTM Stable
LT1677
Single Version of LT1678/LT1679
Rail-to-Rail 3.2nV/√Hz
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, IB = 10pA Max
LT1806
Low Noise, 325MHz Rail-to-Rail Input and Output Op Amp
3.5nV/√Hz
LT1881/LT1882
Dual/Quad Rail-to-Rail Output Picoamp Input Precision Op Amps
CLOAD to 1000pF, IB = 200pA Max
LT1884/LT1885
Dual/Quad Rail-to-Rail Output Picoamp Input Precision Op Amps
2.2MHz Bandwidth, 1.2V/µs SR
C-Load is a trademark of Linear Technology Corporation.
sn16789 16789fs
16
Linear Technology Corporation
LT/TP 0104 1K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2003