square wave oscillator, threshold

Thread Starter


Joined Mar 8, 2011

Square wave oscillator, can someone explain the threshold equation? Also, why only R1 and R2 used?


Joined Feb 12, 2009
R only affects the charging/discharging time of C and therefore the output frequency. It does not affect the threshold.

R1 and R2 function as a potential divider, so that when the output of the amplifier swings from V+ to V-, the voltage on V2 swings by a smaller amount.

When the voltage on the capacitor (V1) reaches the threshold (voltage on V2) the output switches.

Note that the amplifier output will not usually reach V+ or V-. There will be a small voltage drop. See the amplifier data.