TL103WA: Op-Amp Field Failure

Hi Paul,

Sorry about that, I meant to add a schematic (please see attached). I'm not an OpAmp expert so I may need some assistance with what information to provide (hope that is ok)?

TI OpAmp Schematic.pdf

Hi Bret,

We've looked at your schematic and getting some further information on measured voltages or waveforms will be necessary. It is unclear what you mean by "the voltages across the op amp are zero."

Looking at your schematic, we noticed the zener from Pin 3 on U8B to ground. Can you tell us what the part number for that device is or what the Zener voltage is for that diode? That device is internal, sorry for the oversight.

What is the gate voltage on Q10? Does it go low enough to turn off Q10?

Thank you,
Paul

Bret,

I put your schematic into a TINA simulation using an alternate device for the Op Amps. The simulations use the LM358 which is similar in performance to the TL103WA.

On a DC level, the circuit appears to work as desired, toggling the switch changes the output signal KEY. Perhaps you can take a look at the attached schematic and let me know if I misunderstood any part of your design and if you're able to simulate the failure that you're seeing.

Best,

Paul

TL10W_FieldFailureV7.TSC

 Hi Paul,

Thanks for the info. My apologies on the 0 volts across the OpAmp. What I meant was that the comparator reference voltage went down to 0 volts. However, after talking with our EE, he said a few of them went up to the 7.5 volt rail, when it should have been 2.5 volts.

I have passed the information along to our electrical team, and they should have time to look at the information you have provided tomorrow. I will also ask them to provide waveforms and voltages.

Thanks again, 

Hey Ron and Paul,

Thank you for the information. I received the following information from one of our electrical engineers (see attached). I hope this helps with the voltages and wave-forms you requested. Let me know if I can provide any more information.

Thanks again,