LM7321: Negative Bias Supply with grounded Positive supply

Sangbeom Jeong

Part Number: LM7321
Other Parts Discussed in Thread: OPA322, TLV9061

Hello guys.

I have a very simple question of general OPAMP (I'm using LM7321)

Can I use LM7321 while only supply negative power for simple unity gain negative voltage follower ( not negative gain , It is negative input voltage follower for bias buffer )

My circuit setting is

supply V+ : Signal Ground

supply V- : -3V

In+ : Negative Input ( guarantee -2 < Input < -0.5 )

In - : Connected with Out Pin ( for unity gain voltage follower )

I think I have no problems with my configuration. I have some non-opamp no feed back buffers with similar circuit topology (Grounded Positive Supply, Negative Supply Only)

Also, My spice simulation result looks fine with unity gain

Are there any problems I did't noticed?

Thanks for all

over 5 years ago

0 Paul Goedeke over 5 years ago

TI__Mastermind 30600 points

Hi Sangbeom Jeong,

There are no issues with this as long as your input stays between the supply voltages for the amplifier and you want your output signal to be between 0V and -3V. Make sure that your load is terminated to a potential between 0V and -3V as wel.

If your total supply voltage is only 3V though, you might want to consider using a low voltage part like the OPA322 or TLV9061. They'll usually have better low voltage performance and both of those devices have better offset as well.

Best,
Paul

0 Sangbeom Jeong over 5 years ago in reply to Paul Goedeke

Prodigy 100 points

Thank you so much.

In fact, that opamp is used as bidirectional bias voltage source/sink supply (about +/- 50mA)

If you have better solution for bias supply(must sink and source both) please let me know.

Have a good day.

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LM7321: Negative Bias Supply with grounded Positive supply