TL082: Customer used 5 pcs TL082IDR on motor driver but met a Chip fever and output is unstable.

Hi Eggsy,

It would be very helpful if you could provide some further information and be more specific. Can you provide us with scope shots, input signals, desired output signals, and measured output signals? Are there issues on all the circuits or just some?

The schematic seems to indicate that the op-amp used is the TL072 - did they switch to the TL082?

What is "chip fever"?

Thanks,
Paul

Hello Eggsy,

In addition to Paul's comments. Does "Chip fever" mean that the TL082 gets warm or hot to the touch (or thermal camera)?
The schematic shows a lot of circuitry; at what point in the circuit does the output become unstable, larger or smaller than expected?
My first concern is the pole R46 and C27in the top schematic U17C. That likely would be unstable.

Hi Paul,

Yes, they switch all amps to the TL082.
"Chip fever" mean that the TL082 hot to the touch.
input signals, desired output signals is hard to catch the abnormal signal. Because it is Coincidental case that sometime output is smaller than our Expected; sometime output is bigger than our Expected.
Thanks for your help!

There issues on all the circuits

Hi Ronald,

Pole R46 and C27in the top schematic U17C will make it unstable. Do you have any suggestions to deal with it?
Thanks !

Hi Eggsy,

It is really difficult for us to begin debugging unless you can provide more detailed information. Please try to find out more so that we can help you.

Specifically:
* What are the input voltages?
* What are the desired output voltages?
* What are the error output voltages?

A hot device could mean that it is driving a lot of current or that there is a short somewhere. It could also mean that something is incorrectly connected. Have the customer test the nodes of the op-amps to make sure that the supplies are properly connected and not exceeding the abs max values.

Further questions:
* Do the devices get hot all the time? Just sometimes?
* Does every device in the schematic above get hot?
* What is the ambient temperature?
* Do these symptoms happen on many boards or just one?

For stability, try removing C27, C48, and C65. Typically capacitors between the inputs cause problems.

-Paul

Hi Eggsy,

the circuit arround U17A is totally weird... Remove C24 and C27 and swap R43, R44 and R46.

Kai