square wave oscillator, threshold

Thread Starter

uofmx12

Joined Mar 8, 2011
55
Vth=Vcc*(R1/(R1+R2))



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

JDT

Joined Feb 12, 2009
657
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.
 
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