Generate a Pulse Width Modulation/Oscillator

Thread Starter


Joined Apr 7, 2010
Hi everyone,

I have been trying to solve this question (in the Attachment) about generating a PWM.

first i want to understand is this an oscillator circuit but we added (R with vin).

i think know how to analysis the oscillator but what is the difference when we include the vin and R , is it going to affetc the analysis quite alot,i mean there will be an inital voltage on capacitor?.

i am thinking is that at positive terminal e+=V0*(R2/R1+R2),and current start to flow from vo through R and capacitor to ground plus some inital voltage across capacitor,hence at inverting terminal start increas in voltage till a point when the inverting becomes larger than positive terminal, then the state will change over and then capacitor start discharging through the R and vo to zener diode.

in addition how we can design the value of R3.

Any suggestions and any hints would be much appreciated.