LTC1250
Very Low Noise
Zero-Drift Bridge Amplifier
FEATURES
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DESCRIPTIO
Very Low Noise: 0.75µV
P-P
Typ, 0.1Hz to 10Hz
DC to 1Hz Noise Lower Than OP-07
Full Output Swing into 1k Load
Offset Voltage: 10µV Max
Offset Voltage Drift: 50nV/°C Max
Common Mode Rejection Ratio: 110dB Min
Power Supply Rejection Ratio: 115dB Min
No External Components Required
Pin Compatible with Standard 8-Pin Op Amps
Available in Standard 8-Pin Plastic DIP
and 8-Pin SO Packages
The LTC
®
1250 is a high performance, very low noise zero-
drift operational amplifier. The LTC1250’s combination of
low front-end noise and DC precision makes it ideal for use
with low impedance bridge transducers. The LTC1250
features typical input noise of 0.75µV
P-P
from 0.1Hz to
10Hz, and 0.2µV
P-P
from 0.1Hz to 1Hz. The LTC1250 has
DC to 1Hz noise of 0.35µV
P-P
, surpassing that of low noise
bipolar parts including the OP-07, OP-77, and LT1012.
The LTC1250 uses the industry-standard single op amp
pinout, and requires no external components or nulling
signals, allowing it to be a plug-in replacement for bipolar
op amps.
The LTC1250 incorporates an improved output stage
capable of driving 4.3V into a 1k load with a single 5V
supply; it will swing
±4.9V
into 5k with
±5V
supplies. The
input common mode range includes ground with single
power supply voltages above 12V. Supply current is 3mA
with a
±5V
supply, and overload recovery times from
positive and negative saturation are 0.5ms and 1.5ms,
respectively. The internal nulling clock is set at 5kHz for
optimum low frequency noise and offset drift; no external
connections are necessary.
The LTC1250 is available in a standard 8-pin plastic DIP
and 8-pin SO packages.
APPLICATIO S
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Electronic Scales
Strain Gauge Amplifiers
Thermocouple Amplifiers
High Resolution Data Acquisition
Low Noise Transducers
Instrumentation Amplifiers
, LTC and LT are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents
including 4933642.
TYPICAL APPLICATIO
5V
50Ω
GAIN
TRIM
Differential Bridge Amplifier
5V
1000pF
Input Referred Noise 0.1Hz to 10Hz
2
V
S
=
±5V
A
V
= 10k
1
18.2k
µV
0.1µF
350Ω
STRAIN
GAUGE
0
2
–
+
7
6
A
V
= 100
LTC1250
3
4
–1
1000pF
–5V
18.2k
–5V
1250 TA01
–2
U
0
2
6
4
TIME (s)
8
10
LT1250 TA02
U
U
1250fb
1
LTC1250
ABSOLUTE
AXI U RATI GS
Total Supply Voltage (V
+
to V
–
) ............................. 18V
Input Voltage ........................ (V
+
+ 0.3V) to (V
–
– 0.3V)
Output Short Circuit Duration ......................... Indefinite
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec.)................ 300°C
PACKAGE/ORDER I FOR ATIO
TOP VIEW
NC 1
–IN 2
+IN 3
V
–
4
8
7
6
5
NC
V
+
OUT
NC
ORDER PART
NUMBER
TOP VIEW
LTC1250CN8
N8 PACKAGE
8-LEAD PLASTIC DIP
T
JMAX
= 110°C,
θ
JA
= 130°CW
J8 PACKAGE
8-LEAD CERAMIC DIP
T
JMAX
= 150°C,
θ
JA
= 100°CW (J8)
LTC1250MJ8
LTC1250CJ8
OBSOLETE PACKAGE
Consider the N8 or S8 for Alternative Source
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
●
denotes the specifications which apply over the full operating
temperature range, V
IN
=
±5V,
otherwise specifications are at T
A
= 25°C.
SYMBOL PARAMETER
V
OS
Input Offset Voltage
∆V
OS
Average Input Offset Drift
Long Term Offset Drift
Input Noise Voltage (Note 3)
e
n
i
n
I
B
I
OS
CMRR
PSRR
A
VOL
Input Noise Current
Input Bias Current
Input Offset Current
Common Mode Rejection Ratio
Power Supply Rejection Ratio
Large-Signal Voltage Gain
Maximum Output Voltage Swing
Slew Rate
Gain-Bandwidth Product
Supply Current
CONDITIONS
T
A
= 25°C (Note 2)
(Note 2)
T
A
= 25°C, 0.1Hz to 10Hz
T
A
= 25°C, 0.1Hz to 1Hz
f = 10Hz
T
A
= 25°C (Note 4)
●
ELECTRICAL CHARACTERISTICS
T
A
= 25°C (Note 4)
●
SR
GBW
I
S
V
CM
= – 4V to 3V
V
S
=
±2.375V
to
±8V
R
L
= 10k, V
OUT
=
±4V
R
L
= 1k
R
L
= 100k
R
L
= 10k, C
L
= 50pF
No Load, T
A
= 25°C
2
U
U
W
W W
U
W
(Note 1)
Operating Temperature Range
LTC1250M
(OBSOLETE) ............
– 55°C to 125°C
LTC1250C .......................................... 0°C TO 70°C
ORDER PART
NUMBER
NC 1
–IN 2
+IN 3
V
–
4
8
7
6
5
NC
V
+
OUT
NC
LTC1250CS8
S8 PART MARKING
1250
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 110°C,
θ
JA
= 200°CW
●
●
●
●
●
●
LTC1250M
MIN TYP
MAX
±5
±10
±0.01 ±0.05
50
0.75
1.0
0.2
4.0
±50
±150
±950
±100 ±300
±500
110
130
115
130
125
170
±4.0
4.3/–4.7
±4.92
10
1.5
3.0
4.0
7.0
MIN
110
115
125
±4.0
LTC1250C
TYP
MAX
±5
±10
±0.01 ±0.05
50
0.75
1.0
0.2
4.0
±50
±200
±450
±100 ±400
±500
130
130
170
4.3 /–4.7
±4.95
10
1.5
3.0
4.0
5.0
UNITS
µV
µV/°C
nV/√Mo
µV
P-P
µV
P-P
fA/√Hz
pA
pA
pA
pA
dB
dB
dB
V
V
V/µs
MHz
mA
mA
1250fb
LTC1250
The
●
denotes the specifications which apply over the full operating
temperature range, V
IN
=
±5V,
otherwise specifications are at T
A
SYMBOL PARAMETER
f
S
V
OS
∆V
OS
e
n
I
B
I
OS
Internal Sampling Frequency
Input Offset Voltage
Average Input Offset Drift
Input Noise Voltage (Note 3)
Input Bias Current
Input Offset Current
Maximum Output Voltage Swing
Supply Current
Sampling Frequency
CONDITIONS
T
A
= 25°C
T
A
= 25°C (Note 2)
(Note 2)
T
A
= 25°C, 0.1Hz to 10Hz
T
A
= 25°C, 0.1Hz to 1Hz
T
A
= 25°C (Note 4)
T
A
= 25°C (Note 4)
R
L
= 1k
R
L
= 100k
T
A
= 25°C
T
A
= 25°C
LTC1250M
MIN TYP
MAX
4.75
±2
±0.01
1.0
0.3
±20
±40
4.3
4.95
1.8
3
±5
±0.05
LTC1250C
MIN
TYP
MAX
4.75
±2
±0.01
1.0
0.3
±20
±40
4.3
4.95
1.8
3
±5
±0.05
UNITS
kHz
µV
µV/°C
µV
P-P
µV
P-P
pA
pA
V
V
mA
kHz
ELECTRICAL CHARACTERISTICS
●
±100
±200
4.0
2.5
±100
±200
4.0
I
S
f
S
2.5
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
These parameters are guaranteed by design. Thermocouple effects
preclude measurement of these voltage levels during automated testing.
Note 3:
0.1Hz to 10Hz noise is specified DC coupled in a 10s window;
0.1Hz to 1Hz noise is specified in a 100s window with an RC high-pass
filter at 0.1Hz. The LTC1250 is sample tested for noise; for 100% tested
parts contact LTC Marketing Dept.
Note 4:
At T
≤
0°C these parameters are guaranteed by design and not
tested.
TYPICAL PERFOR A CE CHARACTERISTICS
Input Noise vs Supply Voltage
1.6
T
A
= 25°C
1.4
SUPPLY CURRENT (mA)
INPUT NOISE (µV
P-P
)
1.2
1.0
0.8
0.6
0.4
0.1Hz TO 1Hz
0.2
0
4
10
6
8
12
14
TOTAL SUPPLY VOLTAGE, V
+
TO V
–
(V)
16
0.5
0
4
0.1Hz TO 10Hz
4.0
T
A
= 25°C
3.5
SAMPLING FREQUENCY (kHz)
U W
1250 G01
Supply Current vs Supply Voltage
6
Sampling Frequency vs Supply
Voltage
T
A
= 25°C
5
3.0
2.5
2.0
1.5
1.0
4
3
2
10
6
8
12
14
TOTAL SUPPLY VOLTAGE, V
+
TO V
–
(V)
16
4
10
6
8
12
14
+
TO V
–
(V)
TOTAL SUPPLY VOLTAGE, V
16
1250 G02
1250 G03
1250fb
3
LTC1250
TYPICAL PERFOR A CE CHARACTERISTICS
Input Noise vs Temperature
1.2
V
S
=
±5V
1.0
0.8
0.1Hz TO 10Hz
0.6
0.4
0.1Hz TO 1Hz
0.2
0
–50 –25
4.0
4.5
V
S
=
±5V
SAMPLING FREQUENCY (kHz)
SUPPLY CURRENT (mA)
INPUT NOISE (µV
P-P
)
50
25
75
0
TEMPERATURE (°C)
Voltage Noise vs Frequency
80
70
VOLTAGE NOISE (nV/√Hz)
100
V
S
=
±5V
R
S
= 10Ω
GAIN (dB)
50
40
30
20
10
0
1
10
100
1k
FREQUENCY (Hz)
10k
1250 G07
60
GAIN
40
20
0
–20
1k
10k
V
S
=
±5V
OR
SINGLE 5V
T
A
= 25°C
C
L
= 100pF
PHASE:
R
L
= 100k
60
40
BIAS CURRENT (
|
pA
|
)
60
Overload Recovery
8
INPUT (V)
INPUT COMMON MODE RANGE (V)
0.2
0
0
OUTPUT (V)
CMRR (dB)
–5
500µs/DIV
A
V
= 100, R
L
= 100k, C
L
= 50pF, V
S
=
±5V
4
U W
100
1250 G04
Supply Current vs Temperature
8
7
6
5
4
3
2
1
125
2.0
–50 –25
50
25
0
75
TEMPERATURE (°C)
100
125
Sampling Frequency vs
Temperature
V
S
=
±5V
3.5
3.0
2.5
0
–50 –25
0
75
50
25
TEMPERATURE (°C)
100
150
1250 G05
1250 G06
Gain/Phase vs Frequency
100
80
1000
Bias Current (Magnitude) vs
Temperature
V
S
=
±5V
80
PHASE MARGIN (DEG)
100
PHASE:
R
L
= 1k
20
0
100k
1M
FREQUENCY (Hz)
–20
10M
1250 G08
10
–50
–25
50
75
0
25
TEMPERATURE (°C)
100
125
1250 G09
Common Mode Input Range
vs Supply Voltage
140
Common Mode Rejection Ratio vs
Frequency
120
100
80
60
40
20
0
V
S
=
±5V
V
CM
= 1V
RMS
T
A
= 25°C
6
4
2
0
–2
–4
–6
–8
2
3
5
4
6
SUPPLY VOLTAGE (±V)
7
8
1250 G11
1
10
100
1k
FREQUENCY (Hz)
10k
100k
1250 G12
1250fb
LTC1250
TYPICAL PERFOR A CE CHARACTERISTICS
Transient Response
10
9
8
V
S
=
±8V
OUTPUT SWING (V)
2V/DIV
OUTPUT SWING (±V)
1µs/DIV
A
V
= 1, R
L
= 100k, C
L
= 50pF, V
S
=
±5V
Output Swing vs Output Current,
±5V
Supply
5
4
3
OUTPUT VOLTAGE (V)
V
S
=
±5V
5
SHORT-CIRCUIT CURRENT (mA)
2
1
0
–1
–2
–3
–4
–5
0.01
0.1
1
OUTPUT CURRENT (mA)
10
1250 G16
OUTPUT VOLTAGE (V)
TEST CIRCUITS
Offset Test Circuit
100pF
100pF
100k
100k
5V
2
10Ω
3
2
10Ω
–
+
7
6
OUTPUT
LTC1250
4
–5V
1250 TC01
U W
Output Swing vs Load
Resistance, Dual Supplies
18
Output Voltage Swing vs Load
Resistance, Single Supply
16
14
12
V
S
= 10V
10
8
6
4
V
S
= 5V
V
–
= GND
R
L
TO GND
0
1
2
3 4 5 6 7 8
LOAD RESISTANCE (kΩ)
9
10
V
S
= 16V
R
L
TO GND
7
6
5
4
3
2
1
0
0
1
2
NEGATIVE SWING
POSITIVE SWING
3 4 5 6 7 8
LOAD RESISTANCE (kΩ)
9
10
V
S
=
±2.5V
V
S
=
±5V
2
0
1250 G14
1250 G15
Output Swing vs Output Current,
Single 5V Supply
6
V
S
= SINGLE 5V
Short-Circuit Current
vs Temperature
40
30
20
10
0
–10
–20
–30
V
OUT
= V
+
V
S
=
±15V
V
OUT
= V
–
4
3
2
1
0
0.01
0.1
1
OUTPUT CURRENT (mA)
10
1250 G17
–40
–50 –25
0
50
25
75
TEMPERATURE (°C)
100
125
1250 G18
DC to 10Hz Noise Test Circuit
(for DC to 1Hz Multiply All Capacitor Values by 10)
5V
5V
2
6
800k
3
–
+
7
–
8
1
800k
0.04µF
800k
6
–
1/2
LT1057
7
OUTPUT
LTC1250
3
4
–5V
1/2
LT1057
+
4
–5V
5
+
0.02µF
0.01µF
1250 TC02
1250fb
5
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