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PDF INA125U Data sheet ( Hoja de datos )

Número de pieza INA125U
Descripción INSTRUMENTATION AMPLIFIER With Precision Voltage Reference
Fabricantes Burr-Brown Corporation 
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No Preview Available ! INA125U Hoja de datos, Descripción, Manual

INA125
®
INA125
INA125
INSTRUMENTATION AMPLIFIER
With Precision Voltage Reference
FEATURES
q LOW QUIESCENT CURRENT: 460µA
q PRECISION VOLTAGE REFERENCE:
1.24V, 2.5V, 5V or 10V
q SLEEP MODE
q LOW OFFSET VOLTAGE: 250µV max
q LOW OFFSET DRIFT: 2µV/°C max
q LOW INPUT BIAS CURRENT: 20nA max
q HIGH CMR: 100dB min
q LOW NOISE: 38nV/Hz at f = 1kHz
q INPUT PROTECTION TO ±40V
q WIDE SUPPLY RANGE
Single Supply: 2.7V to 36V
Dual Supply: ±1.35V to ±18V
q 16-PIN DIP AND SO-16 SOIC PACKAGES
DESCRIPTION
The INA125 is a low power, high accuracy instrumen-
tation amplifier with a precision voltage reference. It
provides complete bridge excitation and precision dif-
ferential-input amplification on a single integrated
circuit.
A single external resistor sets any gain from 4 to
10,000. The INA125 is laser-trimmed for low offset
voltage (250µV), low offset drift (2µV/°C), and high
common-mode rejection (100dB at G = 100). It oper-
ates on single (+2.7V to +36V) or dual (±1.35V to
±18V) supplies.
The voltage reference is externally adjustable with pin-
selectable voltages of 2.5V, 5V, or 10V, allowing use
with a variety of transducers. The reference voltage is
accurate to ±0.5% (max) with ±35ppm/°C drift (max).
Sleep mode allows shutdown and duty cycle operation
to save power.
The INA125 is available in 16-pin plastic DIP and
SO-16 surface-mount packages and is specified for
the –40°C to +85°C industrial temperature range.
APPLICATIONS
q PRESSURE AND TEMPERATURE BRIDGE
AMPLIFIERS
q INDUSTRIAL PROCESS CONTROL
q FACTORY AUTOMATION
q MULTI-CHANNEL DATA ACQUISITION
q BATTERY OPERATED SYSTEMS
q GENERAL PURPOSE INSTRUMENTATION
V+ SLEEP
VREFCOM 12
1
INA125
2
VREFBG
VREF2.5
13
14
VREF5
15
10V
VREF10 16
4
VREFOut
VI+N
6
9
RG
8
7
VIN
R
R
2R
4R
Ref
Amp
Bandgap
VREF
A1
30k
10k
10k
A2
30k
3
10
11
Sense
VO
VO = (VI+N – VIN) G
G = 4 + 60k
RG
IAREF
5
V–
International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111 • Twx: 910-952-1111
Internet: http://www.burr-brown.com/ • FAXLine: (800) 548-6133 (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
©1997 Burr-Brown Corporation
PDS-1361B
Printed in U.S.A., February, 1998

1 page




INA125U pdf
TYPICAL PERFORMANCE CURVES
At TA = +25°C and VS = ±15V, unless otherwise noted.
60
G = 500
50
G = 100
40
30
G = 10
20
G=4
10
0
1 10
GAIN vs FREQUENCY
100 1k 10k
Frequency (Hz)
100k
1M
COMMON-MODE REJECTION vs FREQUENCY
120
G = 100, 500
100
80
G = 10
60
G=4
40
20
G = 500
G = 100
0
1 10 100 1k 10k 100k 1M
Frequency (Hz)
140
120
100
80
60
40
20
1
POSITIVE POWER SUPPLY REJECTION
vs FREQUENCY
G=4
G = 500
G = 100
G = 10
10 100 1k 10k 100k 1M
Frequency (Hz)
INPUT COMMON-MODE VOLTAGE
vs OUTPUT VOLTAGE, VS = ±15V
15
Limited by A2 output swing—see text
10
5
0
–5
–10
–15
–15
VD/2
VD/2
+
+
–+
VCM
+15V
–15V
VO
IAREF
Limited by A2 output swing—see text
–10 –5
0
5 10 15
Output Voltage (V)
120
100
80
60
40
20
0
1
NEGATIVE POWER SUPPLY REJECTION
vs FREQUENCY
G = 100
G = 500
G = 10
G=4
10
100
1k
10k 100k
1M
Frequency (Hz)
INPUT COMMON-MODE VOLTAGE
vs OUTPUT VOLTAGE, VS = ±5V
5
4
IAREF
=
0V
Limited
by
A2
output
swing—see
text
3
2 VS = +5V
1
0
–1
–2 VS = ±5V
–3
–4 Limited by A2 output swing—see text
–5
–5 –4 –3 –2 –1 0 1 2 3
Output Voltage (V)
4
5
®
5 INA125

5 Page





INA125U arduino
The 60kterm in equation 1 comes from the internal metal
film resistors which are laser trimmed to accurate absolute
values. The accuracy and temperature coefficient of these
resistors are included in the gain accuracy and drift specifi-
cations of the INA125.
The stability and temperature drift of the external gain
setting resistor, RG, also affects gain. RG’s contribution to
gain accuracy and drift can be directly inferred from the gain
equation (1). Low resistor values required for high gain can
make wiring resistance important. Sockets add to the wiring
resistance, which will contribute additional gain error (pos-
sibly an unstable gain error) in gains of approximately 100
or greater.
OFFSET TRIMMING
The INA125 is laser trimmed for low offset voltage and
offset voltage drift. Most applications require no external
offset adjustment. Figure 2 shows an optional circuit for
trimming the output offset voltage. The voltage applied to
the IAREF terminal is added to the output signal. The op amp
buffer is used to provide low impedance at the IAREF
terminal to preserve good common-mode rejection.
VIN
RG
VI+N
INA125
IAREF
VO
V+
100µA
1/2 REF200
OPA237
±10mV
Adjustment Range
10k100
100
INPUT COMMON-MODE RANGE
The input common-mode range of the INA125 is shown in
the typical performance curves. The common-mode range is
limited on the negative side by the output voltage swing of
A2, an internal circuit node that cannot be measured on an
external pin. The output voltage of A2 can be expressed as:
V02 = 1.3VIN – (VI+N – VIN) (10k/RG)
(voltages referred to IAREF terminal, pin 5)
The internal op amp A2 is identical to A1. Its output swing
is limited to approximately 0.8V from the positive supply
and 0.25V from the negative supply. When the input com-
mon-mode range is exceeded (A2’s output is saturated), A1
can still be in linear operation, responding to changes in the
non-inverting input voltage. The output voltage, however,
will be invalid.
PRECISION VOLTAGE REFERENCE
The on-board precision voltage reference provides an accu-
rate voltage source for bridge and other transducer applica-
tions or ratiometric conversion with analog-to-digital con-
verters. A reference output of 2.5V, 5V or 10V is available
by connecting VREFOUT (pin 4) to one of the VREF pins
(VREF2.5, VREF5, or VREF10). Reference voltages are laser-
trimmed for low inital error and low temperature drift.
Connecting VREFOUT to VREFBG (pin 13) produces the
bandgap reference voltage (1.24V ±0.5%) at the reference
output.
Positive supply voltage must be 1.25V above the desired
reference voltage. For example, with V+ = 2.7V, only the
1.24V reference (VREFBG) can be used. If using dual sup-
plies VREFCOM can be connected to V–, increasing the
100µA
1/2 REF200
V–
FIGURE 2. Optional Trimming of Output Offset Voltage.
Microphone,
Hydrophone
etc.
47k
INA125
47k
INPUT BIAS CURRENT RETURN
The input impedance of the INA125 is extremely high—
approximately 1011. However, a path must be provided for
the input bias current of both inputs. This input bias current
flows out of the device and is approximately 10nA. High
input impedance means that this input bias current changes
very little with varying input voltage.
Input circuitry must provide a path for this input bias current
for proper operation. Figure 3 shows various provisions for
an input bias current path. Without a bias current path, the
inputs will float to a potential which exceeds the common-
mode range, and the input amplifiers will saturate.
Thermocouple
INA125
10k
INA125
If the differential source resistance is low, the bias current
return path can be connected to one input (see the thermo-
couple example in Figure 3). With higher source impedance,
using two equal resistors provides a balanced input with
Center-tap provides
bias current return.
possible advantages of lower input offset voltage due to bias FIGURE 3. Providing an Input Common-Mode Current Path.
current and better high frequency common-mode rejection.
®
11 INA125

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