Simple 16 MHz Crystal Oscillator Circuit (High frequency oscillator)

Completed 16MHz crystal oscillator PCB

Here I made a 16 MHz oscillator using crystal. The crystal produce precise frequency signal. This is useful for providing clock signal for digital circuits like ADC, DAC, etc. It is work at 5V supply voltage. So it is useful in every digital circuits. I made it is to provide clock signal for an ADC chip in my next project named "Signal Visualizer".

Crystal

Crystal in PCB

Crystal is a piezoelectric device work based on the piezoelectric effect. In this crystal a piezoelectric element is connected between two metal electrodes. Each piezo element has a resonance frequency. It is determined by the dimension of the crystal element. So when electricity given to the crystal, it is vibrate at its resonance frequency. The resonance frequency is very precise. So this is used for generating high frequency signals.

Circuit Diagram

The circuit diagram is given below.

Circuit diagram

Here I use a 16 MHz crystal, thus it produce a 16 MHz square wave signal. You try with different frequency crystals. Here I use a NOT gate IC 7414 for making the oscillator. It is a TTL IC, which works at 5V supply (greater then 5V damage the IC). It contain 6 individual NOT gates. But here I use only 2 of them. So other 4 NOT gates input is shorted to ground to avoid unwanted noise in the generated signal. The first NOT gate is work as the oscillator and second is act as a buffer to increase the signal power and correct the signal shape. The main part of an oscillator is an amplifier and a feedback system. Here the NOT gate is act like a nonlinear amplifier and the feedback is provided through the crystal. The crystal pass only the 16 MHz signal. So this oscillator only produce a 16 MHz signal in its output (sometime some harmonics preset with lower strength). Here in the circuit diagram the crystal have a 3 legs. It is because it is a symbol of an SMD crystal (I use SMD). So it contain two small valued capacitor connected from two crystal legs and the common leg is the third leg (center leg) of the crystal. It is connected to the ground. If you use ordinary through hole crystal, you connect two 5 pF capacitors from each leg to the ground. If it is not provided, it also works. It is used for stability. The input power-supply capacitor is used for reducing the noise. Try to connect it close to the IC. Also try to connect all the components close to each other.

The output waveform obtained in the DSO (oscilloscope) is given below,

Output waveform in oscilloscope(DSO)

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