I'm working on 16 bit 24 channels DAS. Here are the specs;
Architecture : Single ADC multiple channels. In each channel one AAF is used.
Resolution : 16 bit
Signal swing : +/- 10V (20V)
Input signal frequency : 200Hz max
Number of channels : 24
Total time available for 24 channels for conversion : 800us [ each channel 33us approx]
ADC sampling frequency : 4 MSPS
Line : Differential
Required 3-dB point for AAF : 200 Hz
Order of the filter : 2
Attenuation at 75Khz : -96dB (min)
Settling time: < 2us [ After every selection of channels - It seems to be small when compare to total available time period for each channel (33us). It is because, to increase the per channel sample rate by taking multiple samples of a single channel. 30us is used for sampling each channels.]
AAF architecture: Sallen key
Input allowable offset : <1.2mV
Supply : dual +/-15(min)
24 channels are connected to ADC via MUX(ADG1207). So maximum transient loading occurs during the switching of channels which are connected to max and min value of input signal. Since Sallen-key architecture is used, there may be a need of additional RC filter at the output of AAF opamp.
Can anybody suggest an opamp for this particular application.