Mumbai University > EXTC > Sem 3 > Analog Electronics I

Marks: 5 M

Year: Nov 2013

• In crystal oscillator, the usual electrical resonant circuit is replaced by the piezoelectric crystal
• Crystal oscillator uses mechanical resonance of vibrating crystal of piezoelectric material to generate oscillation of precise frequency
• Every solid material has its own natural resonant frequency. This resonant frequency depends on size, shape, elasticity and the speed of sound in the material.
• Depending on frequency of application, they are cut in different shapes
• The most commonly used crystal is quartz because It is inexpensive and readily available in nature and it exhibits good piezoelectric effect and has a good mechanical strength
• Crystal oscillators are set in oscillations by inverse piezoelectric effect. When a voltage is applied across properly cut quartz crystal surfaces the crystal is distorted by an amount proportional to the applied voltage. An alternating voltage applied to crystal causes it to vibrate at its natural frequency
• The frequency stability of the quartz crystal is excellent. Thermal compensation can be used to improve the thermal stability.
• This are fixed frequency oscillators usually
• Crystal oscillators are used in application where the frequency stability is prime importance
• Crystal oscillators are used in digital integrated circuit to provide stable clock signal., to stabilize frequencies for radio transmitters and receivers, to keep track on time that is in wristwatches also used in oscilloscope, signal generators and counters.