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.
5
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