An opamp Integrator
An opamp Integrator
(OP)
Hello,
I have a simple question regarding op amp integrators. An integrator normally has a capacitor connected between the output and the inverting terminal and this integrates the current coming in to the voltage out. In some circuits I have seen there is a resistor placed in parallel with this capacitor.
What is the purpose of this resistor. Solving for the circuit creates a complicated expression for the output voltage. Please give me some idea.
I have a simple question regarding op amp integrators. An integrator normally has a capacitor connected between the output and the inverting terminal and this integrates the current coming in to the voltage out. In some circuits I have seen there is a resistor placed in parallel with this capacitor.
What is the purpose of this resistor. Solving for the circuit creates a complicated expression for the output voltage. Please give me some idea.





RE: An opamp Integrator
By adding a high valued resistor in parallel to the capacitor you make the DC gain less than infinite and reduces the drift. But you also get some leakage so your integrator will not stay constant any more. But if you need to integrate for a few seconds and if you do read the result within another few seconds then the resistor usually doesn't hurt. For minutes and hours of integration time, you will need good opamps and good capacitors. You also have to pay special attention to leakage currents in the PC board and probably use guard rings around the input pins of your opamps, sometimes even driven by the output via a resistor. Read Jim Williams and Bob Pease. They are quite good at these things.
RE: An opamp Integrator
RE: An opamp Integrator
TTFN
RE: An opamp Integrator
<nbucska@pcperipherals.com>
RE: An opamp Integrator
The books you are asking about were listed in the following thread. Thread240-75845