# trying to understand integrator op amp circuits

Discussion in 'Homework Help' started by RevitRed, Dec 7, 2014.

1. ### RevitRed Thread Starter New Member

Dec 4, 2014
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this is the standard integrator circuit, can someone check if my understanding is correct please

if we assume the the C = 1 mF
the resistor is Rin = 10 kOhms
the op amp will not saturate
ideal op amp
and input voltage is 10 V
trying to figure out voltage out as a function of time

the Vout is supposed to be -1/RC integral(Vin dt)

Vout = -10/(10000 * 10^-3) integral(dt) = -10/(1) = -1t

would this be correct?

so Vout = -10t ?

2. ### MikeML AAC Fanatic!

Oct 2, 2009
5,451
1,066
Since the opamp forces V(inv) to be 0V, the current in the 10K resistor is 1mA (10V/10K). The charge accumulated by the capacitor Q=C(ΔV) = it.
Rearrange, ΔV = it/C = (1e-3)t/1000e-6 = (1e-3)t/1e-3) = t, or 1V/1s. However, the current flow causes the output of the opamp to go negative...

3. ### RevitRed Thread Starter New Member

Dec 4, 2014
6
0
thanks it seems as though your plot has confirmed my answer, by the way what program is it that you used to analyze this circuit

Oct 2, 2009
5,451
1,066