LMH6321: LMH6321 DC SHIFT AT THE OUTPUT

Praveen V

Part Number: LMH6321
Other Parts Discussed in Thread: TINA-TI

Hello Expert,

We are using LMH6321 with a single supply operation. Positive supply V+ for LMH6321 is +15V and Ground pin is at V+/2. With this configuration, there is a 1V of DC shift in the output. Can you please explain how to Remove the DC Shift at the output.

Kindly find the attached Output snap.

Also, With closed loop configuration there is a dc shift at the output. Attached the closed loop Configuration reference circuit.

Regards,

Praveen V

over 3 years ago

0 kai klaas69 over 3 years ago

Guru 140200 points

Hi Praveen,

we would need a schematic :-)

Kai

0 Praveen V over 3 years ago in reply to kai klaas69

Prodigy 50 points

Hi,

Attached the Schematic.

Regards,

Praveen

0 Sima Jalaleddine over 3 years ago in reply to Praveen V

TI__Mastermind 25715 points

Hello Praveen,

Could you measure directly at pin 5 (GND) of the LMH6321 and share the value there?

Thank you,

Sima

0 Praveen V over 3 years ago in reply to Sima Jalaleddine

Prodigy 50 points

Hi,

Voltage at pin 5 of LMH6321 is 7.5V.

Regards,

Praveen V

0 Sima Jalaleddine over 3 years ago in reply to Praveen V

TI__Mastermind 25715 points

Hello Praveen,

It looks like it is railing to V- which is set to ground. This is not a rail to rail amplifier, and from the datasheet this is the voltage output swing for +/-15V:

For your setup, it will have the same headroom for single supplies. Not sure about your load, but at a high load of 1kOhms, the negative output swing minimum is about 1.5ish away from -15V. Therefore for power supplies +15/ground, the swing is: 1.6V to 13.4V.

Thank you,

Sima

0 kai klaas69 over 3 years ago in reply to Praveen V

Guru 140200 points

Hi Praveen,

why not running a TINA-TI simulation?

praveen_lmh6321.TSC

Kai

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LMH6321: LMH6321 DC SHIFT AT THE OUTPUT