AN826 Crystal Oscillator Basics and Crystal Selection for ...

2002 Microchip Technology 1AN826 INTRODUCTIONO scillators are an important component of radio fre-quency (RF) and digital devices. Today, product designengineers often do not find themselves designing oscil-lators because the Oscillator circuitry is provided on thedevice. However, the circuitry is not complete. Selec-tion of the Crystal and external capacitors have beenleft to the product design engineer. If the incorrect crys-tal and external capacitors are selected, it can lead to aproduct that does not operate properly, fails prema-turely, or will not operate over the intended temperaturerange. For product success it is important that thedesigner understand how an Oscillator operates inorder to select the correct of a Crystal appears deceivingly simple.

Steady-state operation of the oscillator is governed by the amplifier and the tuned circuit of the filter block. Loop gain steadies at unity due to the non-linearity of the amplifier. The tuned circuit reactance will adjust itself to match the Barkhausen phase requirement of 2 π radians. During steady-state …

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  States, Basics, Oscillators, Circuit, Crystal, Steady, Crystal oscillator basics

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