Forums » General Electronics Discussion

Well, I am new here, and new to this hobby and I do not know if this the right sub-forum to post my question to.

I have constructed this circuit on a prototyping board:

https://www.circuitlab.com/circuit/875t83/receiver_1_4/

Each amplifier works fine as long as nothing else is connected to the chip. Once I connect a single resistance to the chip, the output of the amplifier goes high. The output on one of the amplifiers rises to 0.5 V while the second falls to -0.5 V. Both work properly but with the mentioned offsets. Now my question(s):

1-Why does this happen? 2-Can I avoid these effects or.. 3-That is normal and I have to eliminate these offsets, or... 4-Probably use two single OP-AMP chips instead

Thanks in advance

PS. I tried using TL084 instead of the LM324: same behavior.

Can you show what you are doing on your CL circuit?

Save your CL circuit under a new name and then add the components you are attempting to describe, run a DC and/or a sim transient and post it here.

If you've actually built it on a physical prototype board then the most likely thing is that you've just made one or more wiring mistakes.

Or it's oscillating.

Got access to a scope?

Can you post a link to a photo?

It is working fine on CL. The problem is in real life. The input signal is DC, something like 20 mV.

Well, I lied....

CL simulation shows identical 270 mV offset for zero input. This is half of what I get at home, and identical for both amplifiers, but it is not zero as I mentioned above. Funny though, I get 0 V when only one amplifier is wired and zero input applied.

Look down in the bottom right of the Editor window when you run your sim ...

Compare with: