AD623
APPLICATIONS INFORMATION
BASIC CONNECTION
the AD623. The +V
S
and −V
S
terminals are connected to the
power supply. The supply can be either bipolar (V
S
= ±2.5 V to
±6 V) or single supply (−V
S
= 0 V, +V
S
= 3.0 V to 12 V). Power
supplies should be capacitively decoupled close to the power pins of
the device. For the best results, use surface-mount 0.1 μF ceramic
chip capacitors and 10 μF electrolytic tantalum capacitors.
+V
S
0.1µF
10µF
The input voltage, which can be either single-ended (tie either
−IN or +IN to ground), or differential is amplified by the
programmed gain. The output signal appears as the voltage
difference between the OUTPUT pin and the externally applied
voltage on the REF input. For a ground-referenced output, REF
should be grounded.
GAIN SELECTION
The gain of the AD623 is resistor programmed by R
G
, or more
precisely, by whatever impedance appears between Pin 1 and
Pin 8. The AD623 is designed to offer accurate gains using 0.1%
to 1% tolerance resistors. Table 5 shows the required values of
R
G
for the various gains. Note that for G = 1, the R
G
terminals
are unconnected (R
G
= ∞). For any arbitrary gain, R
G
can be
calculated by
R
G
= 100 kΩ/(
G
− 1)
+2.5V TO +6V
R
G
OUTPUT
R
G
REF
V
IN
R
G
V
OUT
REF (INPUT)
0.1µF
–V
S
10µF
00778-042
REFERENCE TERMINAL
The reference terminal potential defines the zero output voltage
and is especially useful when the load does not share a precise
ground with the rest of the system. It provides a direct means of
injecting a precise offset to the output. The reference terminal is
also useful when bipolar signals are being amplified because it
can be used to provide a virtual ground voltage. The voltage on
the reference terminal can be varied from −V
S
to +V
S
.
–2.5V TO –6V
Figure 42. Dual-Supply Basic Connection
+V
S
0.1µF
10µF
+3V TO +12V
R
G
OUTPUT
R
G
REF
V
IN
R
G
V
OUT
REF (INPUT)
00778-055
Figure 43. Single-Supply Basic Connection
Table 5. Required Values of Gain Resistors
Desired Gain
2
5
10
20
33
40
50
65
100
200
500
1000
1% Standard Table Value of R
G
(Ω)
100 k
24.9 k
11 k
5.23 k
3.09 k
2.55 k
2.05 k
1.58 k
1.02 k
499
200
100
Calculated Gain Using 1% Resistors
2
5.02
10.09
20.12
33.36
40.21
49.78
64.29
99.04
201.4
501
1001
Rev. D | Page 16 of 24
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