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output of an op amp followed by integrator

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Newbie level 5
Aug 31, 2009
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integrator op am

hello sir,
i am using a circuit in which a capacitor is charging and discharging periodically.during charging of capacitor, the rest of the circuit have no link with the capacitor.when capacitor s discharging cycle comes, one of the electrode is grounded and other goes to the input of a integrator.The integrator is followed by a comparator.Non inverted pins of both are referenced to ground.a current source is used at the input of integrator.a ref cap is used b/w the output of comparator and the inverting terminal of integartor.can you please give me an idea about what type of output i should get at the output.actually this is a test circuit.value of components are not sure to me.

integrator op amp

can you post the circuit

hello sir,
during charging, i m assuming s1 and s3 closed and s2 and s4 be open.And vice versa.i m using current source of value 5mA.Excitation Voltage(Vac) provided to capacitor sensor is 5V.

Curiously, a slightly different version of the same circuit has been posted in another thread.

However, the contributor didn't manage to clarify, how the switches are controlled in the circuit. My assumption has been (and still is), that to operate the circuit in a meaningful way, the comparator output must control the switch timing. Otherwise the integrator output would run into saturation, either positive or negative.

Your circuit can't operate because of inappropriate supply voltages. Particularly, the comparator threshold is outside of the integrator's output voltage range. I wonder, if there are more drawing errors or missing details related to the original circuit.

dear sir,

i have got a mistake.Actually in the real circuit, there is Max987 is used as the comparator.But we were not able to use it in the practical way thats why we dropped using that ic. Will u give some suggestions about the comparator part?what other ic s can we use in the place of max987?What is special property of max987.that is making it to use here.

The said problem isn't caused by the LM339:
comparator threshold is outside of the integrator's output voltage range
LM339 input range includes the negative rail, and so does MAX987.

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