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AD5274 shutdown mode

higherkuo
on Aug 30, 2016

Hi,

I have a question about AD5274 in shutdown mode. From my understanding, the shutdown mode would provide infinity resistance between port A and port W. Am I correct?

I'm using this chip to set the gain of an amplifier. I put the chip to shutdown mode to set to unity gain. (The amplifier is unity gain stable.) However, amplifier output has a high frequency component when I put AD5274 into shutdown mode.

The channel 3 (purple) from the attachment is the output from my amplifier, which should be the inverted version of channel 4 (green). But the half cycle of the output isn't correct.

any idea?

Thanks,

Ye-Sheng

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  • 0 on Jan 24, 2017 10:58 PM

    I have figured out what's going on here.

    The amplifier I'm using is TI INA333, which has strict capacitance requirement on the RG pins. I'm using AD5274 on RG pins to set the gain. However, the intrinsic capacitance on the A and W pins are 1) too high, and 2) not balanced. The INA333 is not stable at half of the waveform. 

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  • 0 on Jan 24, 2017 10:58 PM

    I have figured out what's going on here.

    The amplifier I'm using is TI INA333, which has strict capacitance requirement on the RG pins. I'm using AD5274 on RG pins to set the gain. However, the intrinsic capacitance on the A and W pins are 1) too high, and 2) not balanced. The INA333 is not stable at half of the waveform. 

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