This document introduces Circuit Note CN-0240 Circuits from the Lab™ reference circuits, which are designed to solve analog, mixed-signal, and RF design challenges. The products mentioned in the document include AD629 High Common-Mode Voltage Difference Amplifier, AD8622 Precision, Low Noise, CMOS, Dual, Rail-to-Rail Output Op Amp, AD8475 Precision, Selectable Gain, Fully Differential Funnel Amplifier, etc.
The Analog Devices CN-0240 is a reference circuit designed to monitor bidirectional current from sources with DC voltages of up to ±270 V. It achieves this with less than 1% linearity error using a combination of the AD629 difference amplifier, dual AD8622 op amps, an AD8475 funnel amplifier, and an ADuM5402 quad-channel isolator.
| Maximum DC Source Voltage | ±270 V |
|---|---|
| Linearity Error | < 1% |
| Full-Scale Shunt Voltage | 100 mV |
| Common-Mode Rejection (AD629A) | 77 dB minimum @ 500 Hz |
| Common-Mode Rejection (AD629B) | 86 dB minimum @ 500 Hz |
| End-Point Linearity Error | < 0.5% |
The circuit monitors bidirectional current from sources with DC voltages of up to ±270 V.
The shunt resistor value is chosen so that the shunt voltage is approximately 100 mV at maximum load current.
The primary source of noise is the output noise of the AD629, which is 15 µV p-p in the 0.1 Hz to 10 Hz bandwidth.