PreAmp with 2nd order highpass and differential output

pulser

3rd order lowpass

amp out fz=0

amp out fz=1MHz

filter out fp=15MHz

filter out

amp out

fz=0

Noise tranfer function

amp out

filter out

+ 6dB

Conclusions

- PreAmp for 12 bit resolution = 72 dB SNR and THD

=> 72 dB loop gain + 34 dB closed loop gain = 106 dB @ fT= 40 MHz

- 1 LSB = 245 µV => 310 e @ Cfb = 200fF

- Thermal noise of feedback resistor//capacitor @ Cfb =200fF = 150 µV (kT/C)

- Input referred noise of PreAmp is amplified by A= 1+ Cfb/ Cshunt = ~100 ( 40dB)

=> 150 µV / 100 = 1.5 µV !!! (including pick up)

- Differential input helps to reduce pick up of noise irradiation

- Separate PreAmp chip should be attached very close to detector pad in order to reduce Cshunt

- Pulse shaping by zero of PreAmp transfer function reduces required dynamic range and hence saves power

- High order lowpass (Gm/C) filter is natural companion of AD-converter/digital chip