Quasi-Triangular Pulse Shaping
By summing contributions from the various filter stages in a
semi-Gaussian amplifier, a unipolar output pulse with a much more
linear rise can be generated [Fig. 15(b)]. This pulse shape is
referred to as quasi-triangular because it is a crude approximation
to a true triangular pulse shape. The quasi- triangular pulse
shaping is advantageous at shaping time constants shorter than the
noise corner time constant. Under these conditions, the series noise
component is dominant. Consequently, the quasi-triangular pulse
shape yields approximately 8% lower noise than the semi-Gaussian
pulse shape, with virtually identical dead time per amplifier pulse.
Figure 15. A Comparison
of (a) Semi-Gaussian, (b) Quasi-Triangular, and (c) Bipolar Pulse
Shapes at a 2-µs Shaping Time Contstant.
Vertical scale, 5 V per division; horizontal scale, 2
µs per division. |
