Technical notes about Anti aliasing differential filter- november 2014 R. Assiro - P.Creti

Differential Anti-alias filter Differential Anti-alias filter x5 x1 X1.2 X6 Low G High G ADC Input signal PMT Single channel front-end Input of second stage is fixed to 100 ohms The filter is calculed by elsie 2.72 program with 20 ohm input impedance The maximum filter attenuation is -2dB First stage Second stage -2dB On filter R. Assiro - P.Creti

Filter simulated Filter tested

Output of twin channels (high gain and low gain) on sweep of frequency(input signal -30dBm) Cutoff 60 MHz R. Assiro - P. Creti

Front end type ohm input impedance of second stage amplifier Low gain 0dB high gain 30dB 20 10p 33p51p75p 20N 43N100N 43N 10p 20N 43N 100N 75p51p 33p 100N GND 150 GND ohm already present To obtain the same filter, and the same answer, we must correct the value of the input impedance of second stage of the low gain channel. The high gain channel already has the impedance to 100 ohm R. Assiro - P. Creti