LM324 Voltage Follower problem

Something is wrong with your connections. There should be also 5.93V on the non-inverting input with those resistors. Probably you have mixed up the pins of the IC.

The voltage on the non-inverting input does indeed suggest the IC is defective.

Graham

Seconding Graham's motion -- the LM324 is definitely bad.

If your 20V input is coming from another source, you might want to ensure that there is no voltage input while the LM324 is unpowered. That's one potential cause of this failure. A simple way to do this is to place a 1N914 diode from the input to your LM324 power supply.

If there's a possibility that there are transients on the input voltage, a small (100pF) cap from the junction to GND might also be of help. The LM324 is slow enough that you won't lose much this way. It might help to wire the diode and pF cap directly to the power pins.

And as always, if you're tracking all the way down to GND, make sure to place a load resistor (10K should do) from the op amp output to GND.

Good luck Chris

Yup. Especially power (V+ is pin *4*, GND is pin *11*).

Forgot about that, Most newbies hook up quad op amp power bass-ackwards and hook up an LM317 like a 78XX at least once. But the aroma of the magic smoke teaches well.

Cheers Chris

I have connected +24V to pin no. 4 and Ground to Pin no.11. I am giving this Vcc +24V, after passing through a diode 1N5408. I have connected this to protect my circuit from reverse supply connection.

I also have connected a 10V zener across my input voltage, before giving to the voltage divider.

With the 71K and 30.1K resistor divider, I am getting 1.2V across 30.1K resistor, even if the voltage applied at 71K resistor is 7.5V (Which should be almost 2.2V, by voltage divider rule.)

I will try with connecting load at the output of op-amp.

I will let you know the results....

Thanks!

"Devendra"<

The IC cannot accept negative voltage at the inputs without a negative supply too.

....... Phil

Assuming the 20 V supply is separate from the 24V, did you forget connect the two grounds (20v & 24V) together?

Ed

Thanks for all your suggestions....

I checked all these things and found my circuit ok. I just replaced my Op-amp (On-semi) with a New one (Philips) LM324AD and it started working fine!!

How can I suspect an IC going bad!?

Anyways, my problem got solved....

Thank you all...!

A few years ago, I found LM324 to be prone to failure. Must of been a few bad batches out there. These days, things that I happen to get in repair that still use this chip in newer packages, seem to be more reliable now. The old DIP LM324 packages, I use to find defective in many different products.