Build Your Own Transistor Radios

Chapter 20Resonant Circuits

Resonant circuits, whether they are constructed from capacitors, inductors, ceramic, or quartz materials, play an important role in passing signals in a particular frequency range and attenuating those signals outside the particular frequency range. Generally, resonant circuits are used in oscillators as well as bandpass filters.

Less commonly known, resonant circuits can be used in all-pass networks to provide group delay equalization or phase equalization to band-pass, high-pass, and low-pass filters. The group delay (GD) can be expressed as GD = Δφ/Δω, where Δφ is the change in phase (in radians), Δω is the change in frequency (in radians per second), and ω = 2πf for a plot of the filter in terms of frequency and ...