Burr-Brown INA104CM Very-high accuracy instrumentation amplifier Datasheet

®
INA104
Very-High Accuracy
INSTRUMENTATION AMPLIFIER
FEATURES
DESCRIPTION
● VERSATILE FOUR OP AMP DESIGN
The INA104 is a high accuracy, multistage, integrated-circuit instrumentation amplifier designed for
signal conditioning requirements where very high performance is desired.
A multiamplifier, monolithic design, which uses BurrBrown’s ultra-low drift, low-noise technology, provides the highest performance with maximum versatility at the lowest cost and makes the INA104 ideal for
even high volume applications.
Burr-Brown’s compatible thin-film resistors and lasertrimming techniques are used for minimizing offset
voltage and temperature drift. This advanced technique also maximizes common-mode rejection and
gain accuracy.
The INA104 also contains a fourth operational amplifier, specified separately, which can conveniently be
used for some important applications such as single
capacitor active low-pass filtering, easy output level
shifting, common-mode voltage active guard drive,
and increased gain (x 10,000 and greater).
● ULTRA-LOW VOLTAGE DRIFT:
0.25µV/°C, max
● LOW OFFSET VOLTAGE: 25µV, max
● LOW NONLINEARITY: 0.002%, max
● LOW NOISE: 13nV/√ Hz at f0 = 1kHz
● HIGH CMR: 106dB at 60Hz, min
● HIGH INPUT IMPEDANCE: 1010Ω
● LOW COST
APPLICATIONS
● AMPLIFICATION OF SIGNALS FROM
SOURCES SUCH AS:
Strain Gages
Thermocouples
RTDs
● REMOTE TRANSDUCER AMPLIFIER
● LOW LEVEL SIGNAL CONDITIONER
● MEDICAL INSTRUMENTATION
A3
A4
Output Inverting Input
8
Gain
Gain Sense
–In
14
9
20kΩ
18
10kΩ
10kΩ
10kΩ
10kΩ
A1
17
12
A4 Summing
Junction
11
Feedback
Resistor
26kΩ
CMV Sense
Gain
Gain Sense
+In
4
5
26kΩ
20kΩ
1
10kΩ
A3
A4
A4 Output
10kΩ
5kΩ
A2
2
10
16
15
Offset
Adjust
Offset
Adjust
13
+VCC
3
–VCC
6
Common
7
A4
Non-Inverting Input
International Airport Industrial Park • Mailing Address: PO Box 11400
Tel: (520) 746-1111 • Twx: 910-952-1111 • Cable: BBRCORP •
• Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd. • Tucson, AZ 85706
Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
©1983 Burr-Brown Corporation
PDS-488D
Printed in U.S.A. May, 1995
SPECIFICATIONS—INSTRUMENTATION
AMPLIFIER
At TA = +25°C, VS = ±15V power supply and in circuit of Figure 1 unless otherwise noted.
INA104AM
PARAMETER
MIN
GAIN
Range of Gain
Gain Equation
Error From Equation, DC(1)
Gain Temp. Coefficient(2)
G=1
G = 10
G = 100
G = 1000
Nonlinearity, DC
RATED OUTPUT
Voltage
Current
Output Impedance
1
±10
±5
INPUT OFFSET VOLTAGE
Initial Offset at +25°C(3)
vs Temperature
vs Supply
vs Time
MIN
1000
*
±(0.15 –0.1/G)
2
20
22
22
±(0.002 + 10–5G)
5
100
110
110
±(0.005 + 2 x 10–5G)
+11.5, –12.5
+11.5, –12.5
0.2
±(1 + 50/G)
±(1 + 20/G)
±15
±0.2
±0.1
±5
±0.5
INPUT IMPEDANCE
Differential
Common-Mode
MAX
G = 1 + (40k/RG)
±(0.08 –0.05/G)
±25 ±200/G
INPUT BIAS CURRENT
Initial Bias Current
(each input)
vs Temperature
vs Supply
Initial Offset Current
vs Temperature
*
*
±50 ±400/G
±2 ±20/G
INPUT NOISE
Input Voltage Noise
fB = 0.1Hz to 10Hz
Density, G = 1000
fO = 10Hz
fO = 100Hz
fO = 1kHz
Input Current Noise
fB = 0.01Hz to 10Hz
Density
fO = 10Hz
fO = 100Hz
fO = 1kHz
0.2
±30
*
*
*
*
*
*
±(0.001
+ 10–5G)
MAX
MIN
*
*
*
*
±2
*
±30
UNITS
*
V/V
V/V
%of FS
*
*
*
*
*
±(0.002
+ 10–5G)
*
–10
–11
–11
±(0.001
+ 10–5G)
*
–50
–55
–55
±(0.002
+ 10–5G)
*
*
*
*
*
±5
*
*
±2
*
*
±20
±20
*
*
*
*
µV
µV/°C
µV/V
µV/mo
nA
nA/°C
nA/V
nA
nA/°C
Ω || pF
Ω || pF
*
*
*
*
*
ppm/°C
ppm/°C
ppm/°C
ppm/°C
% of FS, p-p
V
mA
Ω
±10 ±100/G ±25 ±200/G
±0.25 ±10/G
*
*
*
*
*
*
*
MAX
*
*
*
90
106
110
TYP
*
*
*
*
*
±10
V
*
*
*
dB
dB
dB
0.8
*
*
µV, p-p
18
15
13
*
*
*
*
*
*
nV/√Hz
nV/√Hz
nV/√Hz
50
*
*
pA, p-p
0.8
0.46
0.35
*
*
*
*
*
*
pA/√Hz
pA/√Hz
pA/√Hz
300
140
25
2.5
*
*
*
*
*
*
*
*
kHz
kHz
kHz
kHz
20
10
1
200
6.4
0.4
*
*
*
*
*
*
*
*
*
*
*
*
kHz
kHz
kHz
Hz
kHz
V/µs
*
*
30
40
350
40
55
470
*
*
*
*
*
*
*
*
*
*
*
*
µs
µs
µs
30
50
500
45
70
650
*
*
*
*
*
*
*
*
*
*
*
*
µs
µs
µs
®
INA104
TYP
INA104CM
±10 ±100/G ±25 ±200/G
±0.75 ±10/G
*
*
1010 || 3
1010 || 3
INPUT VOLTAGE RANGE
Range, Linear Response
±10
CMR with 1kΩ Source Imbalance
DC to 60Hz, G = 1
80
DC to 60Hz, G = 10
96
DC to 60Hz, G = 100 to 1000 106
DYNAMIC RESPONSE
Small Signal, ±3dB Flatness
G=1
G = 10
G = 100
G = 1000
Small Signal, ±1% Flatness
G=1
G = 10
G = 100
G = 1000
Full Power, G = 1 - 100
Slew Rate, G = 1 - 100
Settling Time (0.1%)
G=1
G = 100
G = 1000
Settling Time (0.01%)
G=1
G = 100
G = 1000
TYP
INA104BM, SM
2
SPECIFICATIONS—OUTPUT AMPLIFIER, A4
At TA = +25°C, VS = ±15V power supply and in circuit of Figure 1 unless otherwise noted.
INA104AM
PARAMETER
MIN
TYP
OPEN-LOOP GAIN, VO = ±100
Rated Load RL ≥ 2kΩ
100
RL ≥ 10kΩ
110
RATED OUTPUT
Voltage at RL = 2kΩ
RL = 10kΩ
Current
Output Impedance
Load Capacitance
(Unity-Gain Inverting)
Short Circuit Current
FREQUENCY RESPONSE
Unity Gain, Small Signal
Full Power
Slew Rate
Settling Time (Unity-Gain)
0.1%
0.01%
10
5
0.35
INA104BM, SM
MAX
MIN
TYP
115
125
*
*
+13, –14.5
+13, –14.5
7.5
2
*
*
INA104CM
MAX
MIN
TYP
*
*
*
*
*
*
dB
dB
*
*
*
*
*
*
*
*
*
V
V
mA
kΩ
*
MAX
UNITS
2000
10
*
*
*
*
pF
mA
1
9
0.55
*
*
*
*
*
*
MHz
kHz
V/µs
*
*
µs
µs
*
37
40
*
*
*
INPUT OFFSET VOLTAGE
Initial, TA = +25°C
vs Temperature
±1
±5
±2
*
*
*
*
*
*
mV
µV/°C
INPUT BIAS CURRENT
+55
+150
*
*
*
*
nA
INPUT IMPEDANCE
Differential
Common-Mode
500
100
RESISTORS, 10kΩ
Accuracy
Drift
Ratio Match
Drift
0.5
30
0.06
5
INPUT VOLTAGE NOISE
fB = 0.1Hz to 10Hz
Density
fO = 10Hz
fO = 100Hz
fO = 1kHz
POWER SUPPLY
Rated Voltage
Voltage Range
Quiescent Current
TEMPERATURE RANGE
Specification:
AM, BM, CM
SM
Operation:
AM, BM, CM, SM
Storage:
AM, BM, CM, SM
θJC
θJA
±5
*
*
5
50
0.12
*
*
*
*
*
*
*
*
*
*
*
*
*
kΩ
MΩ
*
*
*
%
ppm/°C
%
ppm/°C
1.5
*
*
µV, p-p
35
33
32
*
*
*
*
*
*
nV√ Hz
nV√ Hz
nV√ Hz
±15
*
±20
±9.6
*
–25
–55
+85
+125
–55
±8.1
–65
*
*
*
V
V
mA
*
*
*
*
°C
°C
*
*
*
°C
*
*
*
°C
°C/W
°C/W
*
*
*
*
*
*
*
+125
*
+150
*
*
115
130
*
*
*
*
*
* Specifications same as for INA104AM.
NOTES: (1) Typically the tolerance of RG will be the major source of gain error. (2) Not including the TCR of RG. (3) Adjustable to zero at any one gain.
The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes
no responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change
without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant
any BURR-BROWN product for use in life support devices and/or systems.
®
3
INA104
PIN CONFIGURATION
ORDERING INFORMATION
Top View
PACKAGE
TEMPERATURE
RANGE
18-Pin Hermetic DIP
18-Pin Hermetic DIP
18-Pin Hermetic DIP
18-Pin Hermetic DIP
–25°C to +85°C
–25°C to +85°C
–25°C to +85°C
–55°C to +125°C
DIP
MODEL
Gain Sense
1
18 Gain Sense
+In
2
17 –In
INA104AM
INA104BM
INA104CM
INA104SM
– Supply
3
16 Offset Adjust
Common-Mode
Voltage Sense
4
15 Offset Adjust
Gain
5
14 Gain
Common
6
13 +Supply
Non-Inverting Input to A4
7
12 Summing Junction of A4
Output
8
11 Feedback Resistor
MODEL
Inverting Input to A4
9
10 Output of A4
INA104AM
INA104BM
INA104CM
INA104SM
PACKAGE INFORMATION(1)
PACKAGE
PACKAGE DRAWING
NUMBER
18-Pin Hermetic DIP
18-Pin Hermetic DIP
18-Pin Hermetic DIP
18-Pin Hermetic DIP
108
108
108
108
NOTE: (1) For detailed drawing and dimension table, please see end of data
sheet, or Appendix D of Burr-Brown IC Data Book.
ABSOLUTE MAXIMUM RATINGS
Supply ................................................................................................ ±20V
Internal Power Dissipation ............................................................. 980mW
Input Voltage Range ........................................................................... ±VCC
Output Short-Circuit (to ground) .............................................. Continuous
Operating Temperature ................................................. –40°C to +125°C
Storage Temperature ..................................................... –40°C to +125°C
Lead Temperature (soldering, 10s) ............................................... +300°C
ELECTROSTATIC
DISCHARGE SENSITIVITY
This integrated circuit can be damaged by ESD. Burr-Brown
recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and
installation procedures can cause damage.
ESD damage can range from subtle performance degradation
to complete device failure. Precision integrated circuits may
be more susceptible to damage because very small parametric
changes could cause the device not to meet its published
specifications.
USA OEM PRICES
®
INA104
4
MODEL
1-24
25-99
100+
INA118P
INA118PB
INA118U
INA118UB
$5.40
8.10
5.40
8.10
$4.65
7.00
4.65
7.00
$3.85
5.80
3.85
5.80
TYPICAL PERFORMANCE CURVES
At TA = +25°C, VCC = 15V, and in circuit of Figure 1, unless otherwise specified.
CMR vs SOURCE IMBALANCE
GAIN NONLINEARITY vs GAIN
120
G = 100 - 1000
G = 100 - 1000
G = 10
100
G = 10
0.003
Max
CMR (dB)
Gain Nonlinearity (% FS, p-p)
0.01
Typ
G=1
80
G=1
0.001
60Hz
DC
60
0.0003
40
1
10
100
10
1
1k
100
Gain (V/V)
Source Resistance Imbalance (kΩ)
TOTAL OFFSET VOLTAGE DRIFTvs GAIN
GAIN vs FREQUENCY
3200
Output Voltage Drift (µV/°C)
G = 1000
60
Gain (dB)
320
AM
M
,S
BM
32
G = 100
40
G = 10
20
1% Error
G=1
CM
0
3.2
1
10
100
10
1k
100
1k
10k
100k
1M
Frequency (Hz)
Gain (V/V)
GAIN ERROR vs FREQUENCY
CMR vs FREQUENCY
100%
120
G = 100, 1000
G = 10
10%
Gain Error (dB)
CMR (dB)
100
G=1
80
Balanced
Source
G = 1000
1%
G = 100
0.1%
60
G=1
G = 10
0.01%
40
1
10
100
1k
10
10k
100
1k
10k
100k
Frequency (Hz)
Frequency (Hz)
®
5
INA104
TYPICAL PERFORMANCE CURVES
(CONT)
At TA = +25°C, VCC = 15V, and in circuit of Figure 1, unless otherwise specified.
WARM-UP DRIFT vs TIME
QUIESCENT CURRENT vs SUPPLY
±10
8
Quiescent Current (mA)
Change Input Offset Voltage (µV)
10
6
4
2
±9
±8
±7
±6
0
0
3
6
9
12
15
0
±5
Time (Minutes)
±10
±15
±20
Supply Voltage (V)
STEP RESPONSE
SETTLING TIME vs GAIN
1000
G = 1000
+5
Settling Time (µs)
Output (V)
RL = 2kΩ
CL = 1000pF
G=1
+10
0
–5
320
0.01%
0.1%
100
–10
1%
32
0
100
200
300
400
500
600
1
100
Gain (V/V)
OUTPUT NOISE vs GAIN
INPUT NOISE VOLTAGE
vs FREQUENCY (100 ≤ GAIN ≤ 1000)
1k
1000
Input Noise Voltage (nV/√ Hz)
30
Output Noise Voltage (mV, rms)
10
Time (µs)
20
RS = 1MΩ
10
RS = 1000kΩ
RS = 10kΩ
RS = 0
100
10
1
0
1
10
100
1
1k
®
INA104
10
100
Frequency (Hz)
Gain (V/V)
6
1k
DISCUSSION
OF PERFORMANCE
USING THE INA104
Figure 1 shows the simplest configuration of the
INA104. The gain is set by the external resistor, RG,
with a gain equation of G = 1 + (40k/RG). The
accuracy and TCR of RG contribute directly to the gain
accuracy and drift.
For gains greater than unity, resistor RG is connected
between pins 5 and 14. At high gains, where the value of
RG becomes small, additional resistance (i.e., relays,
sockets) in series with RG will contribute to gain error.
Care should be taken to minimize this effect. However,
this error can be virtually eliminated with the INA104 by
using the Gain Sense circuit connection.
Pins 1, 5, 14, and 18 are accessible so that a fourterminal connection can be made to RG. (Pins 1 and 18
are the voltage sense terminals, since no signal current
flows into the operational amplifiers’ inputs.) This is
useful at high gains, where the value of RG is small.
The optional offset adjust capability is shown in
Figure 1. The adjustment affects only the input stage
component of the offset voltage. Thus, the null condition will be disturbed (if input offset is not adjusted
to zero) when the gain is changed. Also, the input
drift will be affected by approximately 0.31µV/°C
per 100µV of input offset voltage that is trimmed.
Therefore, care should be taken when considering use
of the control for removal of other sources of offset.
INSTRUMENTATION AMPLIFIERS
Instrumentation amplifiers are closed-loop gain blocks whose
committed circuitry accurately amplifies the voltage applied
to their inputs. They respond only to the difference between
the two input signals and exhibit extremely high input impedance, both differentially and common-mode. Feedback networks are packaged within the amplifier module. Only one
external gain setting resistor must be added. An operational
amplifier, on the other hand, is an open-loop, uncommitted
device that requires external networks to close the loop.
While operational amplifiers can be used to achieve the same
basic function as instrumentation amplifiers, it is difficult to
reach the same level of performance. Using operational
amplifiers often leads to design trade-offs when it is necessary to amplify low level signals in the presence of commonmode voltages while maintaining high input impedances.
THE INA104
A simplified schematic of the INA104 is shown on the front
pages of this data sheet. It is a three-amplifier device which
provides all the desirable characteristics of a premium performance instrumentation amplifier. In addition, it has features not normally found on integrated circuit instrumentation amplifiers.
The input section (A1 and A2) incorporates high performance, low drift amplifier circuitry. The amplifiers are
connected in the non-inverting configuration to provide the
high input impedance (1010Ω) desirable in the instrumentation amplifier function. The offset voltage and offset voltage
versus temperature is low due to the monolithic design and
improved even further by the state-of-the-art, laser-trimming
techniques.
The output section (A3) is connected in a unity-gain difference amplifier configuration. A critical part of this stage is
the matching of the four 10kΩ resistors which provide the
difference function. These resistors must be initially well
matched and the matching must be maintained over temperature and time in order to retain excellent common-mode
rejection. (The 106dB minimum at 60Hz for gains greater
than 100V/V is a significant improvement compared to most
other integrated circuit instrumentation amplifiers.)
All of the internal resistors are compatible, thin-film nichrome
formed with the integrated circuit. The critical resistors are
laser-trimmed to provide the desired high gain accuracy and
common-mode rejection. Nichrome ensures long-term stability of trimmed resistors and excellent TCR and TCR
tracking. This provides gain accuracy and common-mode
rejection when the INA104 is operated over wide temperature ranges.
The fourth op amp (A4) of the INA104 adds a great deal of
versatility and convenience to the amplifier. It allows easy
implementation of active low-pass filtering, output offsetting, and additional gain generation. The pin connections
make the use of this stage optional and the specifications
appear separately in the table of Specifications.
This circuit may be used as replacement for
the single potentiometer. It will adjust offset
+VCC
and leave drift unchanged.
2N2222
2MΩ
Optional
Offset
Adjust
+VCC
10MΩ
1µF
Tantalum
13
17
18
E1
–In
100kΩ
16
100kΩ
16
15
Gain Sense
14
15
8
INA104
RG
1
2
EOUT
11
5
10
Gain Sense
7
6
(1)
+In
3
EOUT = [1 = (40k/RG)] (E2 – E1)
E2
–VCC
1µF
Tantalum
NOTE: (1) Connect pin 7 to common and pin 10
to pin 11 when Internal Amp A4 is not used.
FIGURE 1. Basic Connection for the INA104 Including
Optional Input Offset Null Potentiometer.
®
7
INA104
+VCC
+VCC
E8 = E6
13
17
13
EOUT = (E2 – E1)(1+ 40k/RG) + VOFFSET
–In
17
18
E1
E1
14
5kΩ INA104
(1)
RG
5
8
7
6
10
EOUT
E2
R2
1kΩ
Reference
8
7
1
12
EOUT
9
5
(1)
A3
Output
6
R3
100kΩ
3
INA104
RG
R1
1MΩ
10
+In
12
14
+15V
1
2
RF
18
2
3
E2
–15V
–VCC
–VCC
A4,
NOTE: (1)
internal to the INA104. External
amp (OPA27 or equivalent) may also be used.
EOUT = (E1 – E2)[(1 + (40k/RG)](RF /10k)
NOTE: (1) A4 inverts the output of the Instrumentation Amplifier,
pin 8 to pin 10. Therefore, the equation for EOUT shows E1 – E2 instead
of E2 – E1.
FIGURE 2. Optional Output Offset Nulling or Offsetting
Using an Amplifier (Low Impedance to Pin 6).
FIGURE 3. Additional Gain From Output Stage.
OPTIONAL OFFSET ADJUSTMENT
PROCEDURE
TYPICAL APPLICATIONS
It is frequently desirable to null the input component of offset
(Figure 1) and occasionally that of the output (Figure 2). The
quality of the potentiometer will affect the results, therefore,
choose one with good temperature and mechanical-resistance
stability. The procedure is as follows:
1. Set E1 = E2 = 0V (be sure a good ground return path exists
to the input).
2. Set the gain to the desired value (greater than 1) by
choosing RG.
3. Adjust the 100kΩ potentiometer in Figure 1 until the
output reads 0V ±1mV or desired setting. Note that the
offset will change when the gain is changed.
4. If the output component of offset is to be removed or if it
is desired to establish an intentional offset, adjust the
100kΩ potentiometer in Figure 2 until the output reads 0V
±1mV or desired setting. Note that the offset will not
change with gain, but be sure to use a stable amplifier with
good DC characteristics. The range of adjustment is ±15mV
as shown. For larger ranges, change the ratio of R1 to R2.
The op amp is used to maintain a low resistance (<0.1Ω)
from pin 6 to Common to avoid CMR degradation.
Many applications of instrumentation amplifiers involve the
amplification of low-level differential signals from bridges
and transducers such as strain gages, thermocouples, and
RTDs. Some of the important parameters include commonmode rejection (differential cancellation of common-mode
offset and noise), input impedance, offset voltage and drift,
gain accuracy, linearity, and noise. The INA104 accomplishes all of these with high precision.
Figure 3 shows how the output stage may be used to provide
additional gain. If gains greater than 1000V/V (10,000 up to
100,000 and greater) are desired, it is better to place some
gain in the output amplifier rather than the input stage due
+VCC
13
EOUT = (E1 – E2)[1 + (40k/RG)] + 2VREF
17
18
E1
11
14
10
BASIC CIRCUIT CONNECTION
The basic circuit connection for the INA104 is shown in Figure
1. The output voltage is a function of the differential input
voltage times the gain. Figure 1 does not include additional
internal op amp A4. Power supply bypassing with a 1µF
tantalum capacitor or equivalent is always recommended.
EOUT
9
5
8
7
1
(1)
6
2
VREF
3
E2
In applications which do not use the fourth internal amplifier
(A4—pins 7, 9, 10, 11, and 12), pin 7 should be connected
to Common and pins 10 and 11 should be connected together. This will prevent the output of A4 from saturating
(“locking-up”) and affecting the offset of the instrumentation amplifier, A1, A2, and A3.
–VCC
–VCC
NOTE: (1) A4 inverts, see Figure 3.
FIGURE 4. Output Offsetting.
®
INA104
INA104
RG
8
+VCC
R
R = a convenient value
(<100kΩ typically)
+VCC
13
17
Shield
–In
18
14
5
E1
4
7
1
2
E2
8
5kΩ INA104
(1)
RG
EOUT
CMV Sense
6
10
+In
3
12
EOUT = [E2 – E1 + (ECM/CMRR)](1 + 40k/RG)
ECM
–VCC
NOTE: Internal Op Amp, A4, or External Amp (OPA27 or equivalent).
FIGURE 5. Use of Guard Drive.
+VCC
+VCC
fP = (1/2πCF104)Hz
CF in farads used with A4.
13
13
CF
17
17
18
18
12
E1(f)
14
E1
10
INA104
RG
5
10
EOUT
(1)
8
7
1
(1)
6
6
2
2
EOUT
9
5
8
7
INA104
RG
9
1
11
14
11
Current Booster
3553 or BUF634
Used with A4
3
3
E2
E2(f)
–VCC
NOTE: (1) A4 inverts, see Figure 3.
EOUT = (E1 – E2)[1 + (40k/RG)][1/(1 + 2πf
104
–VCC
x CF)]
NOTE: (1) A4 inverts. See Figure 3.
FIGURE 6. Active Low-Pass Filtering.
FIGURE 7. Output Power Boosting.
to the low values of RG required (RG < 40Ω for (1 + 40k/RG)
> 1000). Note, however, that accuracy can degrade due to
high amplification of offset, drift, and noise errors.
Output offsetting (“zero suppression” or “zero elevation”)
may be more easily accomplished with the INA104 than
with most other IC instrumentation amplifiers as shown in
Figure 4. The use of the extra internal op amp, A4, means
that CMR of the instrumentation amp is not disturbed, and
that a convenient value of variable resistor can be used. The
circuit shown in Figure 2 can also be used to achieve the
desired offsetting by scaling the resistors R1 and R2. A low
impedance path from pin 6 to Common should be provided
to achieve the high CMR specified. Resistance above 0.1Ω
will cause the CMR to fall below 106dB.
Amplifier A4 also allows active low-pass filtering to be
implemented conveniently with a single capacitor. Filtering
can be used for noise reduction or band-limiting of the
output signal as shown in Figure 6.
The common-mode voltage from the 26kΩ resistors in the
input section appears at pin 4. Figure 5 shows how this
voltage can be used to drive the shield of the input cable.
Since the cable is driven at the common-mode voltage, the
effects of distributed capacitance is reduced and the AC
system common-mode rejection may be improved. Amplifier A4 buffers the CMV at pin 4 from the input cable.
Some typical application circuits are shown in Figures 9
through 11.
®
9
INA104
GENERAL RECOMMENDED HANDLING
PROCEDURES FOR INTEGRATED CIRCUITS
All semiconductor devices are vulnerable, in varying degrees, to damage from the discharge of electrostatic energy.
Such damaging can cause performance degradation or failure, either immediate or latent. As a general practice, we
recommend the following handling procedures to reduce the
risk of electrostatic damage.
2. Ground all operators, equipment, and work stations.
3. Transport and ship microcircuits, or products incorporating microcircuits, in static-free, shielded containers.
4. Connect together all leads of each device by means of a
conductive material, when the device is not connected
into a circuit.
1. Remove static-generating materials, such as untested plastics, from all areas that handle microcircuits.
5. Control relative humidity to as high a value as practical
(50% is recommended).
+VCC
V
Optional Offset Adjust 100kΩ
13
R
Transducer
or Sensor
Shield
Resistance
Bridge
E2
17
R
R
E1
R
–In
15
18
EO = [1 + (40k/RG)] (E2 – E1)
16
14
∆E
8
INA104
RG
IN
+
EOUT
–
5
1
6
2
+In
3
–VCC
FIGURE 8. Amplification of a Differential Voltage From a Resistance Bridge.
+VCC
13
17
Noise
(60Hz Hum)
Shield
E
–In
18
1
14
9
Transducer or
Analog Signal
INA104
RG
5
10
6
Transformer
2
(1)
–VCC
FIGURE 9. Amplification of a Transformer Coupled Analog Signal.
®
INA104
+In
3
NOTE: (1) Guard drive could be used
to improve circuit AC CMR. See Figure 5.
10
EOUT1
7
1
E
2
Noise
(60Hz Hum)
8
11
EOUT2
+15V (from isolated power supply
with bypassing)
13
High voltage protection
diodes are IN459.
+15V
17
E1
330kΩ
G = 1000
–In
18
INA104
14
+15V
LA
RG
40.04Ω
1mVp-p
RA
330kΩ
–15V
8
5
1
RL
–15V
1MΩ
EOUT 1Vp-p
6
CMV
Sense
7
3
To isolation
stage
4
2 +In
E2
5kΩ
(1)
12
10
–15V
(from isolated
1MΩ - 10MΩ power supply
with bypassing)
NOTE: (1) Internal Op Amp, A4, or External Amp (OPA27 or equivalent).
Right Leg Driver Amp gives higher AC CMR.
FIGURE 10. ECG Amplifier or Recorder Pre-Amp for Biological Signals.
17
–In
Isolation Amplifier
18
14
∆EIN
8
INA104
RG
11
5
10
7
1
2
ISO100,
3650,
or
3656(1)
EOUT
3
6
+In
13
–15V(2)
+15V(2)
Input
Common
+15V
Isolated Power Supply
722
+15V
Output
Common
–15V
NOTES: (1) Does not require an external ISO P/S. (2) Bypass as shown in Figure 1.
FIGURE 11. Precision Isolated Instrumentation Amplifier.
®
11
INA104
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