A Unified Analysis of the Signal Transfer Characteristics of a Single-Path FET-R-C Circuit

Tetsuya IIZUKA  Asad A. ABIDI  

IEICE TRANSACTIONS on Electronics   Vol.E101-C   No.7   pp.432-443
Publication Date: 2018/07/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E101.C.432
Type of Manuscript: INVITED PAPER (Special Section on Analog Circuits and Their Application Technologies)
Sampling,  sample-and-hold,  passive mixer,  sampling oscilloscope,  N-path mixer,  signal flow graph,  frequency translation,  conversion gain,  noise figure,  input impedance,  

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A frequently occurring subcircuit consists of a loop of a resistor (R), a field-effect transistor (FET), and a capacitor (C). The FET acts as a switch, controlled at its gate terminal by a clock voltage. This subcircuit may be acting as a sample-and-hold (S/H), as a passive mixer (P-M), or as a bandpass filter or bandpass impedance. In this work, we will present a useful analysis that leads to a simple signal flow graph (SFG), which captures the FET-R-C circuit's action completely across a wide range of design parameters. The SFG dissects the circuit into three filtering functions and ideal sampling. This greatly simplifies analysis of frequency response, noise, input impedance, and conversion gain, and leads to guidelines for optimum design. This paper focuses on the analysis of a single-path FET-R-C circuit's signal transfer characteristics including the reconstruction of the complete waveform from the discrete-time sampled voltage.