3 Preamplifier Response
Figure 3 shows the response of the preamplifier to a signal when in electrons mode. The signal is
positive going so the preamplifier must be biased at about 0.7V to give maximum dynamic range.
The rise time of the preamplifier will be determined by the detector capacitance and the Miller
compensation setting. If there were no channel reset, the preamplifier would take several 100
microseconds to recover for large signals. However, there is a reset and the delay before the reset is
programmable. Worst case data rates should be 5kHz/channel with an occupancy of 15%.
Response of Preamp to signal in Electrons Mode
Signal Amplitude
VPRE~0.7
VPRE~0.7
Recovery Time ~100s of m s
Signal Amplitude Reset
Programmable Reset Delay
Figure 3: Electron mode transient response.
The Miller compensation should be set to minimise the rise time while keeping the amplifier stable.
This will depend on the input capacitance and therefore the detector strip length. The capacitance
can vary from a few pF up to 80pF.
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