Self-biasing for FET-driven microwave VCOs

摘要

A microwave voltage-controlled oscillator includes a varactor-controlled tuned circuit connected to the gate of an FET. The gate of the FET forms a Schottky barrier contact with the channel region. This Schottky barrier operates to clip the RF voltages generated in the gate circuit, and this clipping is used to provide the necessary gate bias to set the operating point of the VCO. No other source of bias is provided, and thus no DC return path from the gate circuit to the source or drain of the FET exists. Thus, the other circuit elements normally required to establish the gate operating point, which would have high frequency resonances, are eliminated. This permits operation of a microwave VCO over an extremely broad bandwidth.