I'm trying to understand integrator circuit timing, specifically at the point of op amp saturation. Here's my circuit:
The op amp is dual supply +/-12V.
Vin is a square wave varying from -5V to +5V with a 50% duty cycle and period of 40ms - slow enough so that
Vout will reach saturation. Here's the simulation output:
Here's my understanding:
At 6ms the op amp reaches negative saturation voltage and can no longer maintain 0V (virtual ground) at its negative input.
V(R3) is still 5V so current flows into
C1 (it can't flow into the "infinite" impedance op amp input). As charge collects at
C1 its voltage increases meaning less current flows through
What is the formula for calculating the time taken for
V(R3) to drop to zero? Is it just
5RC (which is 5ms) and tallies with the simulation or do I have to take into account the fact that there's charge already accumulated on
C1 plates due negative voltage at
Additionally, what happens when
Vin changes to -5V (at 21ms). What's the formula for calculating the time taken for
V- to reach zero?