Synchronous detection circuit and method for determining a bio-impedance of a biological tissue

Embodiments of synchronous detection circuits and methods are provided for extracting magnitude and phase information from a waveform. One embodiment of a synchronous detection circuit includes a driver circuit, an analog-to-digital converter (ADC) and a controller. The driver circuit is configured to supply an input waveform at an input frequency to a load. The ADC is coupled to receive an outputwaveform from the load, and configured for generating four digital samples, each spaced 90 DEG apart, for every period of the output waveform. The controller is configured for setting an oversamplingrate (OSR) of the ADC, so that the ADC generates an integer number, M, of sub-samples for each digital sample generated by the ADC, where the integer number, M, of sub-samples is inversely proportional to the input frequency of the input waveform. The controller is further configured to use the digital samples generated by the ADC to extract magnitude and phase information from the output waveform. 本申请公开提供用于从波形提取幅度和相位信息的同