AnsweredAssumed Answered

"hello world" circuit with op42

Question asked by JMGL on Sep 24, 2013
Latest reply on Sep 25, 2013 by JMGL

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