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"hello world" circuit with op42

Hello guys,

Sorry for this post, I am guessing it is extreamly basic but I just cannot get around it.

I am using an op42, The connections are:

1 (NULL) -> Not connected

2 (-IN)     -> through 10k to (6) and through 10k to signal

3 (+IN)    -> GROUND

4 (V-)      -> GROUND

5 (NULL) -> Not connected

6 (OUT)  -> through 10k to (2) and output

7 (V+)     -> ~5V

8 (N.C.)  -> Not connected

This is the simplest inverting cicuit that I could make. I was just playing with the op to learn how to use it. The signal is a square function from 0 to 1.5V.

The output of that configuration, I was expecting to be the inverted signal, nevertheless, what I obtain is a square signal with really small pk to pk and with an offset of 1.5V.

I have also tried with other resistors pairs (100R and 100R) and what I get is a DC voltage with the input signal on top.

Searching the web, they recomended to use a compensating resitor (with resistance equal to the parallel equivalent of the other two resistors) between (3) and GROUND, but this did not change anything at all.

Do you have any idea of what I am doing wrong?

Thank you

JMGL

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  • Hi Marcos,

    The part should be able to handle +/-15V. If your part is getting hot, you might have a short in the circuit. What power supply are you using? It's always a good idea to check the current on the power supply to see that you're not drawing too much - about 6mA is expected out of the OP42. Try double-checking your connections just to make sure you're not pulling any power pins or the output to ground. Also check that you have the feedback circuit at the Vin- pin.

    If you have these things checked out, with either the inverting or the non-inverting configuration and using dual supplies (stick with +/-12V or +/-15V as Harry suggested), the best way to start out would be to input a DC voltage and see if it's being amplified correctly.

    Let me know how it goes!

    Kris

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  • Hi Marcos,

    The part should be able to handle +/-15V. If your part is getting hot, you might have a short in the circuit. What power supply are you using? It's always a good idea to check the current on the power supply to see that you're not drawing too much - about 6mA is expected out of the OP42. Try double-checking your connections just to make sure you're not pulling any power pins or the output to ground. Also check that you have the feedback circuit at the Vin- pin.

    If you have these things checked out, with either the inverting or the non-inverting configuration and using dual supplies (stick with +/-12V or +/-15V as Harry suggested), the best way to start out would be to input a DC voltage and see if it's being amplified correctly.

    Let me know how it goes!

    Kris

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