CMOS

FIGURE 6.22 CR-RC shaper with finite feedback resistor in the CSA.

6.6    POLE-ZERO CANCELLATION AND BASELINE CONTROL

We have assumed so far that the feedback resistor of the charge sensitive amplifier does not give any contribution to the signal shape. This is an over-simplification, because even large values of R_f result in visible effects on the impulse response of the front-end. For simplicity, we study this issue for the case of the CR-RC shaper shown in Fig. 6.22, but the conclusions we will derive are qualitatively valid for unipolar shapers of any order. The following parameter values, resulting in a gain of 100 mV/fC with a δ-like input, ...