Schematic, PCB, simulation results, firmware and outputs for 20MHz oscilloscope.
Specification was for an anti-aliasing filter suitable for the 40MSPS maximum sample rate.
To be implemented with a minimum of a first-order 20dB per decade response and ±2dB maximum ripple in the pass band.
The plot below shows these specifications were satisfied. A flat response (-13.8 to -13.7dB) can be seen in the pass band, giving a ripple of less than 2dB.
The 3dB cut-off point is at 20Mhz (-16.5dB) allowing for a maximum sampling rate of 40MSPS. The response can be seen to drop off by 20dB per decade.
Input signal: 50kHz, 2v pk-pk
Output signal: 50kHz, 2v pk-pk
