21.twenty(a) is normally known as the Pierce crystal. The ensuing circuit frequency of oscillations is about through the sequence resonant frequency in the crystal. Variations in supply voltage, transistor parameters, and so on. have no impact on the circuit functioning frequency which happens to be held stabilized via the crystal. https://timing-components-for-con93838.blogsmine.com/35342938/crystal-oscillator-things-to-know-before-you-buy