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A ceramic resonator is an electric component that exhibits a series resonant and a parallel resonant center frequency. It exhibits a piezoelectric characteristic that makes the ceramic material generate minute electrical energy when subjected to electromechanical expansion and compression. The resulting mechanical energy component produces the electric component and vice versa, and the result is a complex reactance that leads to resonance observed as the characteristic of having a center frequency. Materials such as lead zirconium titanate have a ceramic piezoelectric characteristic.
Oscillators are electronic circuits that generate periodic waveforms. The ceramic resonator may be used as a frequency reference in the electronic oscillator, wherein the accuracy of the resulting frequency is not as high as in the crystal oscillator. Error in frequency for the ceramic resonator circuit may be as high as 5%, while that for the crystal oscillator is less than 0.1%.
The ceramic resonator may also be used for intermediate frequency (IF) amplifier stages, which are found in heterodyne radio receivers that derive a common IF to receive a sub-band of frequencies. For instance, a radio receiver tuned to 1,000 kilohertz (kHz) or 1,000 cycles per second may generate a local oscillator frequency of 1,455 kHz so that the difference is 455 kHz, which is a typical IF frequency. To receive a 1,500 kHz signal, the local oscillator is tuned to 1,955 kHz and the resulting difference is still 455 kHz. This ceramic resonator is tuned or cut to resonate at around 455 kHz and will serve a sub-band like 550 to 1,600 kHz as in a typical amplitude modulation (AM) band.
A typical ceramic resonator has three terminals. The two main terminals are at each wide side of a thin ceramic material, while the middle terminal is usually connected to the thin side and may be grounded or used to tap signal into the rest of the oscillator circuit. There are, however, ceramic resonators as well as crystal resonators with only two terminals.
Amplifiers are the active parts of the oscillator. The ratio of the output voltage to the input voltage of an amplifier is known as the voltage gain, which is dependent on the frequency of interest. Very few amplifiers will maintain a constant gain over a wide range of frequency. When a ceramic resonator controls the oscillator frequency, the voltage gain at the ceramic resonator frequency has to be greater than 1. If the voltage gain is less than 1, the amplifier will not start oscillating.
In electronics, design amplifiers and oscillators have very common components. With design shortcomings, some amplifiers can be very close to oscillating. Meanwhile, some oscillators may just stop oscillating and behave like idle amplifiers. Ideally, amplifiers do not have output when there is no input signal.
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