AD8215

Data Sheet

Rev. B | Page 10 of 13

THEORY OF OPERATION

In typical applications, the AD8215 amplifies a small differential

input voltage generated by the load current flowing through a

shunt resistor. The AD8215 rejects high common-mode voltages

(up to 65 V) and provides a ground-referenced, buffered output

that interfaces with an analog-to-digital converter (ADC).

Figure 26 shows a simplified schematic of the AD8215.

V+

OUT =

G = +20

AD8215

A1

R1

R

PROPRIETARY

OFFSET

CIRCUITRY

GND

Figure 26. Simplified Schematic

A load current flowing through the external shunt resistor

produces a voltage at the input terminals of the AD8215. R and

R1 connect the input terminals to A1. The inverting terminal,

which has very high input impedance, is held to

because negligible current flows through R. A1 forces the

noninverting input to the same potential. Therefore, the current

that flows through R1 is equal to

output buffer amplifier has a gain of 20 V/V and offers excellent

accuracy as the internal gain setting resistors are precision trimmed

to within 0.01% matching. The resulting output voltage is equal to