Response of Preamp to signal in Holes Mode
Recovery Time ~100s of m s
VPRE~2.3
Signal Amplitude
Programmable Reset Delay
VPRE~2.3
Signal Amplitude
Reset
Figure 4: Holes mode transient response.
The response of the preamplifier to signals in holes mode is shown in figure 4. In this case, the signal
is negative going so the preamp should be biased at about 2.3V. The dynamic range of the
preamplifier is the same in both holes and electrons modes.
On occasion there may be large signals in the region of 1GeV and the circuit needs to able to recover
from this. The channel reset goes some way to doing this however there is an overload recovery
circuitt which automatically protects the preamplifier against large signals.
A summary of the specification is shown below:
 Signal polarity – either electrons or holes. (programmable)
 Coupling to detectors – DC.
 Detector leakage current – 0-100nA, typically 20nA, both polarities. Automatically
controlled.
 Detector capacitance – variable, from few pF up to ~ 80pF.
 Overload recovery – within 10us for 1GeV signal.
 Data rate – Dependent on position in detector. Worst case: 5kHz/channel
 Occupancy – Dependent on position in detector. Worst case: 15%
 Energy range – 0-50MeV.
 Lowest energy to be measured – 40keV.
 Resolution and noise threshold – 8keV RMS (19keV FWHM).
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