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swuster
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Homework Statement
Look up the offset current for the LM353 op-amp and predict the time rate of change of the output for the circuit below after the switch opens. (Find dVo/dt)
Homework Equations
offset current = 50 pA
i+ = i-, ideally
v+ = v-, ideally
The Attempt at a Solution
I really don't know where to begin. Vo = V- in this case, so I think the 50 pA are flowing through the other branch. When the switch is flipped, the capacitor discharges, losing voltage. But how can I derive dV/dt when ideal op-amps have infinite gain?
[edit] Had some more insight on this, but still want to check to see if it's right:
If the gain of the op amp is A:
I = C dV(+)/dt
dV+/dt = 5 V/s
Vo = A(v+ - v-) = A(v+ - Vo)
Vo = v+ * A / (1 + A)
dV0/dt = dv+/dt * A / (1 + A)
If A is large then A / (1 + A) = 1 so dV/dt = 5 V/s.
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