OPA2354: POWER SUPPLY

David Zhao

Intellectual 1820 points

Part Number: OPA2354

Please help with below question about OPA2354 V+/V-. Thanks!

Is it ok to connect V+ to GND and connect V- to negative 3V?

Regards

David

over 7 years ago

0 Sean Cashin over 7 years ago

TI__Genius 17576 points

Hi David,

Yes, since voltage is just a measure of potential between two points. The op amp will operate identically for Vcc=3V and Vee=0V, Vcc=0V and Vee=-3V, and Vcc=-50V and Vee=-53V, assuming the input voltage range is also scaled within the (V-)-0.1 min and (V+) +0.1 max rating found in the Electrical Characteristics section 7.7 of the datasheet. However, if a voltage greater than Vs+0.5V (>.5V in your case) is applied to the amplifier input, this would exceed the absolute Maximum Rating for voltage in section 7.1 and damage the amplifier.

Best regards,

Sean

0 David Zhao over 7 years ago in reply to Sean Cashin

TI__Intellectual 1820 points

Hi Sean

Thanks for reply!

So for below application. When VIN1 and VIN2 is -3V to 0v. Then also able to get -3V to 0v based on below schematic, right? Thanks!

0 Sean Cashin over 7 years ago in reply to David Zhao

TI__Genius 17576 points

See below.

0 Sean Cashin over 7 years ago in reply to Sean Cashin

TI__Genius 17576 points

Apologies David,

I didn't notice that the Voltage Output Swing from Rail is (V+)-.1V typ and (V+)-.3V max. In the max case, that means the highest output voltage possible is (V+)-.3V. Even though the -3V~0V input voltage is within bounds from (V-)-.1V ~ (V+)+.1V, the output voltage limitation will clip the unity gain signal down to (V-) ~ (V+)-.3V.

Best regards,

Sean

0 David Zhao over 7 years ago in reply to Sean Cashin

TI__Intellectual 1820 points

Hi Sean

Noted. Thanks!

Regards

David

0 David Zhao over 7 years ago in reply to Sean Cashin

TI__Intellectual 1820 points

Hi Sean

One quick question, if just use one channel, the other is not used. So connect the unused input to GND or float is ok? Thanks!

Regards

David

0 Sean Cashin over 7 years ago in reply to David Zhao

TI__Genius 17576 points

Hi David,

Ideally, you would connect it to common mode, or (Vcc+Vee)/2. Grounding and leaving it floating will put the output at one of the rails, and it will consume an extra .5mA or so of current. However, this might be acceptable in your case.

Best regards,

Sean

0 David Zhao over 7 years ago in reply to Sean Cashin

TI__Intellectual 1820 points

Hi Sean

Thanks for response!

Then if grounding or floating will cause any self-oscillation issue? Thanks!

Regards

David

0 Sean Cashin over 7 years ago in reply to David Zhao

TI__Genius 17576 points

Hi David,

No, it won't cause oscillation, just a DC operating point at a rail.

-Sean

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OPA2354: POWER SUPPLY