Transcript PZ1 chip (PZ0 modified to drive 50W terminated cables at 77K)

Gerda phase II Front-End: resistorless ?
BEGe or segmented detectors  electrode cap of a few pF
Mounting of the front-end
devices in the style used in
ultra low noise X-ray
spectrometers might be
appropriate in order to
exploit det low capacitance
A few devices are
mounted very close to
the electrode, while
the remaining part of
the preamplifier
is
placed at some distance
as connected with thin
twisted-pair or coaxial
cables
Very FE to be placed very close to detector electrode
FE devices include FET, CF, CTEST, RF. Chip resistors in the GW range have the
poorest radio purity  a resistorless preampliflier could be best suited
Resistorless preamplifiers in literature
Low-noise charge preamps with no feedback resistor are found in
literature as developed for X-ray spectroscopy
How does the feedback capacitance get discharged ?
1. FBF. This solution uses the gate-to-source forward biased FET junction to
provide discharge current path (G.Bertuccio, P. Rehak, D. Xi, NIM A326, pp. 71-76, 1993)
2. BJT. This solution uses the transversal parasitic BJT of dual gate FET’s to
provide discharge current path (P. Rehak, A. Fazzi, NIM A439, pp. 391-402, 2000)
3. MOSFETa. This solution uses a MOSFET in weak inversion in parallel to CF
(P.O’Connor, G. Gramegna, P. Rehak, et al, IEEE Trans. Nucl. Sci, vol. 44, no. 3 pp. 318-325, 1997)
4. MOSFETa + NL P/Z. This solution adds a non-linear Pole-Zero (P/Z)
compensation to previous solution (G. Gramegna, P. O’Connor, P. Rehak, S. Hart, NIM A390, pp. 241-250, 1997)
5. MOSFETb. This solution uses a MOSFET to discharge CF through a negative
feedback loop (B. Ludewigt, J. Jaklevic, I. Kipnis, et al, IEEE Trans. Nucl. Sci., vol. 41, no. 4, 1994)
6. PULSED. This solution forces the preamplifier reset when its output crosses
a preset threshold, or at fixed clocked times
Resistorless preamplifiers in literature
• 1 and 2 are easy-to-implement as discrete-component
circuits
• 3, 4 and 5 are integrated circuits
• 6 can be realized with discrete components or as an
integrated circuit
None of the shown circuits has been tested at cryogenic
temperatures
Resistorless preamplifiers in literature
Problem: g-ray spectroscopy requires much better
linearity than X-ray spectroscopy. Can existing
resistorless solutions be used ?
Solution 4 shown in the list is the best candidate
as it uses a technique to eliminate the
nonlinearities of the reset device
A study on existing/new solutions for resistorless charge
preamplifiers suited for g-spectroscopy is needed and
challenging
Resistorless preamplifiers in literature
2
ENC=13 el rms
1
ENC=19 el rms
3
5
4
ENC=40 el rms
ENC=9 el rms
ENC =
19 el rms
Technical details can be found in the quoted papers