Abstract: In this paper, a technique is proposed to implement
an artificial voltage-controlled capacitance or inductance which can
replace the well-known varactor diode in many applications. The
technique is based on injecting the current of a voltage-controlled
current source onto a fixed capacitor or inductor. Then, by controlling
the transconductance of the current source by an external bias voltage,
a voltage-controlled capacitive or inductive reactance is obtained.
The proposed voltage-controlled reactance devices can be designed
to work anywhere in the frequency spectrum. Practical circuits for the
proposed voltage-controlled reactances are suggested and simulated.