Скачать или смотреть Capacitor Multiplier Op Amp Circuit: How does it work?

A programmable capacitor multiplier op amp circuit is analyzed in this circuit video. This circuit is effectively implementing a varactor or variable capacitor whose capacitance is defined and set by a control voltage applied in the circuit. Two operational amplifiers and one N-channel JFET Transistor (Junction Field Effect Transistor) are used to design this circuit. The drain-source resistor of JFET can be set between as low as 25 and is a function of its Gate-Source voltage controlled by the Vcontrol. A combination of virtual short of op amp, Kirchhoff Circuit Laws including KCL and KVL are used to analyze this circuit. The equivalent input impedance of the overall circuit is purely capacitive with a capacitance value that is a multiplied or scaled value of the core capacitor in the circuit.