Oscillators
The digital oscillator is a positive feed back amplifier. For an amplifier output voltage Vout = A*Vin (input voltage) where A if forward gain. Similarly feedback voltage Vf = B*Vout (output voltage).
Get Tashi George’s stories in your inbox
Join Medium for free to get updates from this writer.
From the above two equations, Vout = AB*Vin.
The behavior of the output wave depends upon the AB.
If AB<1, it amplifies the noise.
If AB=1, the output is sustained.
If AB>1, The output signal damps.
Thermal noise present in a circuit contains all frequency components. The amplifier circuit acts as a frequency selector, ie a feedback path having only one frequency with zero phase shift.
In a digital oscillator, the amplifier circuit is designed in such a way that initially AB>1 amplifies the thermal noise of frequency. Once amplitude equals to the desired value is achieved then it behaves as if AB=1. The feedback can be made from RC, LC or crystal.
