Datasheet
AD623
Rev. D | Page 16 of 24
APPLICATIONS INFORMATION
BASIC CONNECTION
Figure 42 and Figure 43 show the basic connection circuits for
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.
00778-042
R
G
R
G
V
IN
OUTPUT
V
OUT
REF
R
G
REF (INPUT)
+2.5V TO +6V
+
V
S
10µF0.1µF
–2.5V TO –6V
–V
S
10µF0.1µF
Figure 42. Dual-Supply Basic Connection
00778-055
R
G
R
G
V
IN
OUTPUT
V
OUT
REF
R
G
REF (INPUT)
+3V TO +12V
+
V
S
10µF0.1µF
Figure 43. Single-Supply Basic Connection
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)
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
.
Table 5. Required Values of Gain Resistors
Desired Gain 1% Standard Table Value of R
G
(Ω) Calculated Gain Using 1% Resistors
2 100 k 2
5 24.9 k 5.02
10 11 k 10.09
20 5.23 k 20.12
33 3.09 k 33.36
40 2.55 k 40.21
50 2.05 k 49.78
65 1.58 k 64.29
100 1.02 k 99.04
200 499 201.4
500 200 501
1000 100 1001