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AD8283 Filter Response

Question asked by MikeZ on Apr 9, 2013
Latest reply on Apr 22, 2013 by MikeZ

My question concerns the filter response in Figure 14. on page 11 of the AD8283 datasheet.  I have been testing this A/D converter and the programmable gain amplifiers, channel selection through SPI, digitization etc.. all seem to be working within specs, except for the programmable third order low-pass filter.  According to Figure 14, for a cutoff frequency of 1 MHz, there is an attenuation of 28 dB at 2 MHz, since at 1 MHz the gain is ~16 dB and at 2 MHz the gain is ~ -12 dB.  To test the filter response, the output of the AD8283 was connected to a D/A converter and the output signal was observed.  The A/D was programmed to have a cutoff frequency of 1 MHz, however, as the input signal frequency (into A/D) was increased from 1 MHz to ~ 2 MHz, the output of the D/A didn't change in amplitude whatsoever.

 

Thanks in advance

MikeZ

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