AD8236

Rev. 0 | Page 18 of 20

APPLICATIONS INFORMATION

AC-COUPLED INSTRUMENTATION AMPLIFIER

An integrator can be tied to the AD8236 in feedback to create a

high-pass filter as shown in Figure 41. This circuit can be used

to reject dc voltages and offsets. At low frequencies, the impedance

of the capacitor, C, is high. Therefore, the gain of the integrator

is high. DC voltage at the output of the AD8236 is inverted and

gained by the integrator. The inverted signal is injected back into

the REF pin, nulling the output. In contrast, at high frequencies,

the integrator has low gain because the impedance of C is low.

Voltage changes at high frequencies are inverted but at a low

gain. The signal is injected into the REF pins, but it is not enough to

null the output. At very high frequencies, the capacitor appears as

a short. The op amp is at unity gain. High frequency signals are,

therefore, allowed to pass.

pass filtered input signal.

AD8236

AD8603

R

+IN

–IN

0.1µF

0.1µF

10µF

REF

C

1

2πRC

Figure 41. AC-Coupled Circuit