Crystal oscillator are used for obtaining output signal with stable frequency. Because they provide highly stable frequency they are used in RF radio circuits and for clocking devices such as microcontrollers. Here it is shown how to make a simple crystal oscillator. The presented crystal oscillator has also many advantages and is reliable. It is simple because it can be build using only few components. The advantage of this oscillator is that it can be used for quartz crystal from 2 to 20MHz and operated from 3V to 15V power supply. The oscillator frequency can even reach higher value with corresponding quartz crystal.
The following picture shows the crystal oscillator build on a breadboard.
And the schematic of the oscillator is below.
This oscillator circuit is called Pierce Crystal Oscillator which is variant of Colpitts oscillator. The resistor R3 provides a path for the feedback signal before the oscillation starts and also biases the transistor. Here popular general purpose transistor 2N3904 is used which performs the amplification of the output from the oscillation produced by the crystal.
The oscillator can be easily build on breadboard in just few minutes. In the test, a 4MHz quartz crystal, 11.05MHz crystal and an unknown frequency crystal was tested. We can view the signal waveform output of the oscillator by placing probe on the collector. The following shows the probe on the collector and the signal waveform from the 4MHz quartz crystal based oscillator on oscilloscope.
The following video demonstrates the testing of the crystal oscillator.
So in this way this tutorial showed how to make simple Crystal Oscillator and test it.
