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# Can't get the OpAmp working

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#### DoTan

##### New Member
Hi Guys

I am working on a private project where I need to detect a blue light flashing up. But the OpAmp I am using is always on HIGH regardless of the brightness of the blue light. I have also tried various OpAmp circuits but they all resulted in the same. I've tried feedback resistors of up 100MOhms.
What can I do to make it work, if it is even possible to fulfill?

The Sensor I'm using
The OpAmp I'm using (TL052CP)

Looking forward to any kind of help.
Cheers

I have also tried various OpAmp circuits but they all resulted in the same.
Well, show us a schematic of the circuit which you used and we may be able to help.

A generic "it does not work" gives no clues whatsoever.

JimB

Well, show us a schematic of the circuit which you used and we may be able to help.

A generic "it does not work" gives no clues whatsoever.

JimB

Yes, JimB, you're right. Sorry.

I basically tried this:
(SOURCE: https://i.stack.imgur.com/)
I've tried various resistor sizes ranging from 10MOhms to 100MOhms (10*10 in series)
+VSS 5V and -VSS 0V

+VSS 5V and -VSS 0V
I think that could be your problem.

Read the first couple of pages of the datasheet.
These op-amps require +/- 5 volts, ie 10 volts total supply voltage.

If you are using a unipolar power supply, ie 0v and +10v, the inputs and outputs should be referred to a virtual ground which is set to about +5v

As a simple solution to get you going, I suggest that you use a bipolar supply of at least +/-5v.

JimB

Try two 9V batteries for a +-9V supply. The output is inverting for the configuration shown, but you can flip the polarity of the input.

Vos, Ib and unity gain stable are the three most important parameters. Being able to zero the OP-amp helps a little too.

Don't forget 0.1 uf ceramic bypass capacitors.

A metal film or polyester cap in parallel with the feedback resistor helps. fc=1/(2*PI*R*C); fc is corner frequncy, R is the FB resistor and C is capacitance in Farads.

You may need to put a high value resistor in series with the + and - input. >10K-100K.

I built plenty of these things including one for measuring quantum efficiency of a solar cell.

Common Mode Input Voltage Range. It is a little hard to read the datasheet but, The inputs do not work if the voltage is too close to the negative supply. They will not work at or near the negative supply. They need to be above the supply by about 2.5V. The inputs can run near the positive supply.

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