TYPICAL PERFORMANCE CURVES (CONT)
At TA = +25°C, VS = ±15V, unless otherwise noted.
CMR vs FREQUENCY
POWER SUPPLY REJECTION
10 100 1k 10k 100k
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.
– VOUT = 10(V3 –V2)
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
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.
at pin 1. See text.
VO = V2 – V3
Offset Adjustment Range = ±3mV
FIGURE 2. Offset Adjustment.
Referring to Figure 1, the CMR depends upon the match of
the internal R4/R3 ratio to the R1/R2 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.