OPA855: can we use Power Down mode for OPA855 for practical application.

Jatin Wanjari

Part Number: OPA855

I had simulated a TIA using OPA855 (in Tina TI) which I'm powering up by split power supply of +/-2.5V. According to datasheet "when the amplifier is configured with ±2.5-V supplies, then the threshold voltages for disable and enable are at –1.85 V and –0.7 V."

So, there are 2 types of Gain curve I'm getting for AC analysis in disabled and enabled mode:

1. 15dB gain with 4Ghz BW (when OPA855 is disabled -> PD pin voltage is -2.5V).

2. approx. 50dB gain with 2.5GHz BW (when OPA855 is enabled -> PD pin voltage is +2.5V).

Both the Bandwidth are obtained with different feedback resistors values.

Is it feasible to use disabled mode of OPA855 for practical application to obtain higher bandwidth?

over 5 years ago

0 Michael Steffes over 5 years ago

Guru 48395 points

Well Jatin,

Disabled you are likely seeing just some form of feedthru - not a real amplifier in that mode - probably should not depend on it,

0 Jatin Wanjari over 5 years ago in reply to Michael Steffes

Prodigy 20 points

Dear Michael,

Thank you for your response.

Is it possible that due to disabled mode, the only gain I'm obtaining is due to the open loop gain of OPA855.

0 Michael Steffes over 5 years ago in reply to Jatin Wanjari

Guru 48395 points

Are you talking sim or on the bench?

In sim, the shutdown is a real problem to get that doing everything correctly - I believe ADI rarely tried to support that feature in the sim models and perhaps TI is moving that way as well.

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OPA855: can we use Power Down mode for OPA855 for practical application.