Circuit unit

Abstract

The invention relates to the technical field of amplifiers, in particular to a circuit unit of a compensation radio frequency field-effect tube and a nonlinear capacitor. The circuit unit comprises a voltage source, a switching diode, a decoupling capacitor and a varactor diode, wherein the voltage source and the switching diode are in series connection, the circuit in series connection and the decoupling capacitor are in parallel connection, the circuit in parallel connection and the varactor diode are in series connection, the circuit in series connection and a field-effect tube to be compensated are in parallel connection, and both the negative electrodes of the switching diode and the varactor diode are connected with the decoupling capacitor. When the compensation circuit unit and the field-effect tube are in parallel connection, the change rule of the overall equivalent capacitance in parallel connection to drain-source voltage of the field-effect tube is more gentle, so that the modulation phenomenon of a resonant amplification circuit of the radio frequency field-effect tube is effectively suppressed.

Description

technical field [0001] The invention relates to the technical field of amplifiers, in particular to a circuit unit for compensating the nonlinear capacitance of a radio frequency field effect tube. Background technique [0002] The drain-source equivalent capacitance of the FET varies with the voltage between the drain and the source. The higher the voltage, the smaller the capacitance, and its variation law has nonlinear characteristics, such as figure 1 shown. [0003] If the FET is used in a resonant amplifier circuit, the drain-source equivalent capacitance is connected in parallel with the resonant tank and is a part of the resonant tank capacitance. As the voltage instantaneous value of the amplified waveform changes, the resonant capacitance also changes. Due to the nonlinearity of the change of the resonant capacitance, when the resonant circuit and the amplifier load are under certain conditions, the FET resonant amplifier circuit will self-excited oscillation, re...

AI Technical Summary

Problems solved by technology

[0004] This phenomenon deteriorates the output waveform of the amplifier and reduces the working stability and load adaptability

When the drain-source voltage is low, the equivalent capacitance changes drastically, so the waveform modulation phenomenon is easy to occur when the FET is working at low voltage

In order to alleviate this phenomenon, the usual practice is to avoid the FET working in a low-voltage state, which will limit the working range of the entire amplifier circuit.

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