Frequency Response

Resistance, inductance, capacitance, voltage and current are important parameters in an electrical circuit. Amplifier and filter circuits use these parameters to produce the gain and alter the circuit characteristics with different frequencies. When dealing with AC circuits, the source frequency is generally held constant at 50 Hz or 60 Hz. If this frequency is varied, by keeping a constant magnitude of the source of a circuit, the frequency response of this circuit can be obtained. The frequency response of a circuit provides information on how the output behaviour of the circuit, in terms of magnitude and/or phase, changes with the change in the operating frequency. Generally, a circuit’s frequency response is obtained by plotting its frequency-dependent gain (also known as transfer function) versus frequency. In this chapter, attention is given to the topics of (i) variation of resistance, inductance and capacitance with frequency, (ii) transfer function, (iii) filter circuits, and (iv) resonance, bandwidth and Q-factor for series and parallel circuits.