The working circuit delivers a voltage from pin 6 to the Mosfet regardless whether theirs a voltage at the drain of the mosfet or not . it makes no difference . With the good op amps installed the whole project works when a voltage and current is supplied to the control board. The bad op amps lock the mosfets full on and can not be controlled.
The bad op amps deliver 9v continuously At pin 6 with 0 volts applied to pin 3 . With 0 volts applied to pin 3 on the bad chips there is still 250mV coming from pin 3.
Considering that when the good op amps are installed the whole project works as it should . So I think I have a pretty good idea of what I'm doing.
Can you please either (1) annotate your schematic with pin numbers or (2) refer to the signal names. Without digging out a datasheet we've no idea what signal is on what pin.
To enable sane discussion I've edited your quotes with pin numbers substituted for signal names and obvious typos corrected.
The bad op amps deliver 9v continuously at the output (pin 6) with 0 volts applied to the non-inverting input (pin 3) .
Yup, the output at positive saturation just as I predicted. The op amp doesn't need to be bust for that to happen, I would
expect it as long as there was some input offset voltage present because you've no effective feedback loop with no power applied to the mosfet sources. What's telling here is that you're not telling us what voltage is on pin 2 (the inverting input) at the same time. For this particular op amp V
out = (V
pin3 - V
pin2) * 100,000, so a 90 uV difference between the two inputs is enough to drive the output to the rail. The typical input offset voltage is specified as 2 mV, 22 times more than is needed to force saturation.
This MUST be a typo:
With 0 volts applied to the non-inverting input (pin3) on the bad chips there is still 250mV coming from the non-inverting input (pin 3).
If you mean the
output instead of the
non-inverting input then, again, with no effective feedback loop you cannot predict what voltage will be there.
Considering that when the good op amps are installed the whole project works as it should . So I think I have a pretty good idea of what I'm doing.
What constitutes "works as it should"? That is, what are the signal conditions that you are taking as "works"?
You keep claiming that you have "a pretty good idea of what I'm doing" or similar but all appearances suggest otherwise and that you're blaming "bad op amps" for a failure to understand how this circuit should work. Folks are trying to help, but we can't if all you do is say 'I know what I'm doing' when offered explanations and advice. Please convince us that you're not clueless and that you understand the basics of this circuit by answering one question: What is the transconductance of this whole circuit (from the control input to the source of the mosfets)?
Yes, this is a deliberate shibboleth and you should be able to answer it in 5 seconds if you know what you're about. If you can't then
please listen to what people are saying.