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PGA2320: Frequency response

Part Number: PGA2320

Hi,

I have test the audio amplifier PGA2320 like this:

I adjust the PGA to 31.5dB over SPI and I put a Frequency generator at the input of the PGA.

After that, I adjust the frequency generator to a sine wave 1KHz and the ampitude I adjust that the output of the PGA have 10Vpp.

Now I change only the frequency of the frequency generator to 1/10/20/40Khz.

The Unity-Gain Bandwith is 1MHz according to the datasheet, page 2 "electrical characteristics".

So I guess that the output aplitude of the PGA should be equal 10Vpp over this frequency  area, but the output of the PGA depends of the frequency.

1KHz=10Vpp/10KHz=9,2Vpp/20KHz=7,4Vpp/40KHz=5,7Vpp

Why do I have a behavior like this?

Thanks and Best, Daniel

  • Hi Daniel,
    From the unity gain bandwidth if 1MHz, I'd expect to see around a 26.6kHz bandwidth at maximum gain, since 31.5dB gives a gain of ~37, I'd expect the unity-gain bandwidth to be reduced by about this same factor.

    It looks like your data matches this estimate of the -3dB point , since you measured 31.5dB at 1kHz, 30.8dB at 10kHz, 28.9dB at 20kHz, and 26.6dB at 40kHz.