Semiconductor tuning circuit having constant Q over a wide range

A new type of variable tuning circuit using semiconductor inductance is described. This tuning circuit has a constant Q value over a wide range of frequency. Semiconductor inductance in this circuit is obtained using the impedance conversion method, however, there is no instability such as with negative impedance converter (NIC) and the structure of the circuit is simple. The common fault of semiconductor inductances is that their input impedance changes according to frequency, causing the Q value to vary widely. An attempt to solve this fault by the addition of a second ganged capacitor was made. Experimental results prove the validity of the theory, and confirm that this tuning circuit has practical applications. Applications of this circuit are shown at the end of this paper.