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what affect the Negative Resistance in oscillation circuit?

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leocyh

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hello i hope someone can answer my question.

i am now checking the -R of an oscillation circuit and found that the -R is quite low (probably around 60 ohms). i am wondering is the value of -R depended on, let say the IC i use or something else? how can i increase the -R of this oscillation circuit? The crystal that I am using in this circuit is around 80 ohms BUT I DO NOT WANT TO CHANGE THE CRYSTAL.

thank you for your answer! :D
 

For sinusoidal oscillators, you want the negative resistance to just cancel out the positive resistance in the rest of the circuit. If the negative resistance is too much larger, then the output waveform starts to grow without bounds. This amplitude increase will continue until some non-linear limit is reached. Typically, this limit is the power supply rail.
Therefore, with too much negative resistance you get a square wave output.
 

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