1 Introduction

Isolated amplifiers are essential building blocks in systems that require electrical isolation of two parts of a circuit. Isolated amplifiers allow transferring analog signals across the isolation barrier. In principle, isolated amplifiers are high-end precision analog-to-digital (ADC) and digital-to-analog (DAC) converters with a digital isolator in one package. On the primary side (input) a delta-sigma modulator converts the input signal into digital data. Capacitive isolation then transfers this data across the isolation barrier. The circuitry on the secondary side (output) converts the digital data back into an analog voltage.

The most common versions of isolated amplifiers feature a fully differential output as shown in Figure 1-1. This configuration is beneficial in systems where the common mode (CM) noise can interfere with the signal chain between the amplifier and the analog-to-digital converter. However, in systems where the CM noise is not a concern, the single-ended output isolated amplifier (Figure 1-2) eliminates the need for a difference amplifier, typically required with the differential outputs. A good example is the AMC0330 family of voltage sensing devices that offer both output types.