Datasheet

INA106
5
SBOS152A
www.ti.com
TYPICAL PERFORMANCE CURVES (CONT)
At T
A
= +25°C, V
S
= ±15V, unless otherwise noted.
POWER SUPPLY REJECTION
vs FREQUENCY
Frequency (Hz)
PSRR (dB)
140
120
100
80
60
40
1
10 100 1k 10k 100k
V–
V+
CMR vs FREQUENCY
Frequency (Hz)
CMR (dB)
110
100
90
80
70
60
10
100 1k 10k 100k
APPLICATIONS INFORMATION
Figure 1 shows the basic connections required for operation
of the INA106. Power supply bypass capacitors should be
connected close to the device pins as shown.
FIGURE 1. Basic Power Supply and Signal Connections.
The differential input signal is connected to pins 2 and 3 as
shown. The source impedance connected to the inputs must
be equal to assure good common-mode rejection. A 5Ω
mismatch in source impedance will degrade the common-
mode rejection of a typical device to approximately 86dB. If
the source has a known source impedance mismatch, an
additional resistor in series with one input can be used to
preserve good common-mode rejection.
The output is referred to the output reference terminal
(pin 1) which is normally grounded. A voltage applied to the
Ref terminal will be summed with the output signal. The
source impedance of a signal applied to the Ref terminal
should be less than 10Ω to maintain good common-mode
rejection.
Figure 2 shows a voltage applied to pin 1 to trim the offset
voltage of the INA106. The known 100Ω source impedance
of the trim circuit is compensated by the 10Ω resistor in
series with pin 3 to maintain good CMR.
V
2
25
6
INA106
V
OUT
= 10(V
3
–V
2
)
1
R
4
100kΩ
V
3
R
1
10kΩ
R
3
10kΩ
3
R
2
100kΩ
1µF
V–
1µF
V+
47
+
–
FIGURE 2. Offset Adjustment.
V
2
25
6
INA106
V
O
1
R
4
R
1
R
3
3
R
2
499k
Ω
100
Ω
100k
Ω
+15V
–15V
V
3
10
Ω
V
O
= V
2
– V
3
Offset Adjustment Range = ±3mV
Compensates for
some impedance
at pin 1. See text.
Referring to Figure 1, the CMR depends upon the match of
the internal R
4
/R
3
ratio to the R
1
/R
2
ratio. A CMR of 106dB
requires resistor matching of 0.005%. To maintain high
CMR over temperature, the resistor TCR tracking must be
better than 2ppm/°C. These accuracies are difficult and
expensive to reliably achieve with discrete components.