High Common-Mode Voltage,
Programmable Gain Difference Amplifier
AD628
FEATURES FUNCTIONAL BLOCK DIAGRAM
REXT2
+VS
7 –IN 8 G = +0.1
–IN The AD628 is a precision difference amplifier that combines
excellent dc performance with high common-mode rejection
over a wide range of frequencies. When used to scale high
voltages, it allows simple conversion of standard control
voltages or currents for use with single-supply ADCs. A
wideband feedback loop minimizes distortion effects due to
capacitor charging of Σ-Δ ADCs.
A reference pin (VREF) provides a dc offset for converting bipolar
to single-sided signals. The AD628 converts +5 V, +10 V, ±5 V,
±10 V, and 4 to 20 mA input signals to a single-ended output
within the input range of single-supply ADCs.
The AD628 has an input common mode and differential mode
operating range of ±120 V. The high common mode, input
impedance makes the device well suited for high voltage
measurements across a shunt resistor. The inverting input of
the buffer amplifier is available for making a remote Kelvin …