1-33 Resonance RESONANCEis a condition that exists in a circuit when inductance, capacitance, and the applied frequency are such that inductive reactance and capacitive reactance cancel each other. Formula for resonant frequency (f_{r}): NOTE: The formula for resonance is the same for series or parallel circuits when X_{L}= X_{C}. Transistors Semiconductor devices that have three or more elements are called TRANSISTORS. The term is derived from TRANSfer and resISTOR. This term describes the operation of the transistor — the transfer of an input signal current from a low-resistance circuit to a high-resistance circuit. Some transistor formulas are shown below. Transistor total current: