- Oscillators with LC feedback circuits
An LC Oscillator converts a DC input into an AC output. This output waveform can have a wide range of different shapes and frequencies, and can be either complex in shape, or be a simple pure sine wave depending upon the application. An Oscillator is basically an Amplifier with Positive Feedback, or regenerative feedback and one of the many problems in electronic circuit design is stopping amplifiers from oscillating while trying to get oscillators to oscillate. Oscillators work because they overcome the losses of their feedback resonator circuit either in the form of a capacitor, inductor or both in the same circuit by applying DC energy at the required frequency into this resonator circuit. In other words, an oscillator is a an amplifier which uses positive feedback that generates an output frequency without the use of an externally applied input signal.
- Piezoelectric materials and their applications
Crystal Oscillators, A piezoelectric crystal will vibrate naturally in several mechanical modes, the frequencies of vibration being dependent on the dimensions of the specimen and the elastic constants of the material (f = 1/2l √Y/√ρ). If the crystal is placed between electrode and an alternating voltage at one of the resonant frequencies is applied, the amplitude of oscillation will build up at this frequency.
Transducer, Acoustic pulses are used in underwater search and other applications. In almost all such cases the acoustic pulses are produced by piezoelectric transducers shock excited by electric fields.
Delay Lines, the piezoelectric materials can be used as delay lines. If an electrical signal is converted into an acoustic one at one end of a quartz rod, the signal will pass along the rod as an acoustic wave. It will travel in the quartz with the appropriate sound velocity. On reaching the end of the rod, the acoustic wave may be picked off as an electrical signal. The initial electrical signal has been delayed; a requirement often found in communication devices.