INA849: Minimum load impedance

ILYA FERSHTATER

Part Number: INA849

Tool/software:

Hi,

What is minimum active load impedance for INA849 instrumentation amplifier (i.e. what is minimum Rload)?

The electrical parameters in the data sheet presented for Rload=10 kohm. Is it typical value? Can I use Rload=2 kohm or smaller, even 1 kohm?

3 months ago

0 Ashley Kang 3 months ago

TI__Genius 14350 points

Hi Ilya,

What is the desired output swing range of your application? And what supply voltage are you using? The lower the load impedance, the higher output current and this will limit the available output swing range.

Regards,
Ashley

0 ILYA FERSHTATER 3 months ago in reply to Ashley Kang

Prodigy 20 points

Hi Ashley,

The desired output swing range is about 300mVpk-pk. In any case not exceeding 1Vpk-pk. The supply voltages = +/- 5V. In my calculations I took maximum output current Isc=+/- 34mA and divided it by factor of 10. So 5V/3.4mA=1.5kohm. Is that correct?

Best regards,

Ilya

+1 Ashley Kang 3 months ago in reply to ILYA FERSHTATER

TI__Genius 14350 points

Hi Ilya,

The output short circuit current spec in the datasheet is a condition when the output is connected to Vs/2 which in this case is ground. This is the max output current the amplifier can source or sink, but the output will be saturated. The calculation method you used will give some guardband, and is for the condition if your output swings to the rail.

For the minimum load resistance, I would recommend using a load greater than 625ohms, please see the typical graph below showing THD vs Freq with different load configurations.

Please let me know if you have further questions.
Thank you!

Regards,
Ashley

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INA849: Minimum load impedance