OPA657 in die form

Ankur Shah

Other Parts Discussed in Thread: OPA657, OPA653, OPA659, OPA656

I am using OPA657 as TIA in the die form.

On my PCB, I have a TIA followed by a unity gain OPA657 amplifier to drive the Load.

Initially, I am using the 2 stages as voltage amplifier on PCB. APD is not connected yet.

Out of the 5 PCB's that we mounted the components on, 3 PCB outputs are sensitive when I shine Red light on the OPA657 die.

Is OPA657 in die form vulnerable to light? If yes, why only on 3/5 PCB outputs? The output starts jumping and becomes unstable.

over 13 years ago

0 Xavier Ramus over 13 years ago

TI__Expert 4950 points

Hello Ankur,

The OPA657 is a decompensated amplifier, meaning that it is not unity gain stable, so I am somewhat puzzled when you mentioned that you are using it as a buffer to drive the load. For unity gain stable FET amplifier, consider using the OPA656 or the OPA659. A FET buffer optimize for gain of 2V/V is the OPA653. In that stage, the noise of the amplifier will not add significant contribution to the overall noise, so that spec should be relaxed.

You should see a voltage on the output if you shine a light on a die, but I would not expect an oscillation.

Also for the TIA, the APD parasitic capacitance is part of the compensation as at high frequency, the gain will be set by 1+Cf/Cs, so a lower input capacitance than what the amplifier expects for stability will yield an unstable amplifier.

Best regards,

Xavier

0 David Rocek over 9 years ago in reply to Xavier Ramus

Prodigy 50 points

Hello, can you advise where to get OPA657 in DIE form? We would like to use it in our application but TI is not offering it. Or?

0 David Rocek over 9 years ago

Prodigy 50 points

Hi, can you recommend where to get OPA657 in DIE form? We would like to use it in our application but TI is not offering it, or?

0 Samir Cherian over 9 years ago in reply to David Rocek

TI__Genius 12631 points

Hello,
The OPA657 is not currently sold in die form. Can you please let me know who the customer is and the expected volume and I can work with the planning and development team to see if it is feasible.
-Samir

0 David Rocek over 9 years ago in reply to Samir Cherian

Prodigy 50 points

Hi Samir,

the customer is EU company and annual volume about 20Ku.

David

0 Samir Cherian over 9 years ago in reply to David Rocek

TI__Genius 12631 points

Thanks David,
I am working with the planning teams now to see what we need to do to make this happen. I hope to get back to you next week.
-Samir

0 David Rocek over 9 years ago in reply to Samir Cherian

Prodigy 50 points

Hi Samir,

any update here? I am still waiting for your feedback.

Please let me know when we could expect it.

Thank you.

Best regards,

David

0 Amit Goyal over 9 years ago in reply to David Rocek

TI__Prodigy 240 points

Hi David,

We are looking into supporting die form for OPA657. We will confirm feasibility during next week. Can you please send your contact email information so that we can directly discuss with you.

Thanks,

Amit

0 David Rocek over 9 years ago in reply to Amit Goyal

Prodigy 50 points

Dear Amit,

here is my e-mail: .

Please, do not share it in the forum. Thank you.

Best regards,

David

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OPA657 in die form