US Patent 7557655 Systems and methods for isolating an analog signal

An accurate linear equivalent of an analog signal may be produced across an isolation barrier by driving a primary transformer winding with a drive amplifier and compensation amplifier, where the compensation operational amplifier amplifies a difference between a signal produced on a sense winding of the transformer and a combination of the input analog signal and output of the drive amplifier. The system may be stabilized by a lead-lag network between the sense winding, input signal, and operational amplifier. The transformer may comprise an isolation barrier to isolate the input analog signal from a signal winding. The primary winding of the transformer, driven by the operational amplifier and driver amplifier circuit, may produce a linear equivalent of the input analog signal across the isolation barrier on a signal winding of the transformer. The transformer may comprise power supply windings connected to a power supply bridge rectifier and regulator circuit to control and supply power to the circuit components across the isolation barrier. The operational amplifier and drive amplifier circuit may be active for only a portion of each analog signal sampling period. The control signals may provide power during the rest of the sampling cycle.