Preamplifier

The preamplifier boosts the SiPM's very small signal amplitude by ~20dB and should be located as close as possible to the SiPM itself in order to maintain an acceptable signal-to-noise ratio (SNR). Therefore, a plug-on PCB for the SiPM board in the same form factor was designed, which shall be as versatile as possible in order to adapt for different read-out concepts with the following properties:

• supply of the SiPM bias voltage through the preamp including bias filter
• AC-coupling of the preamp input
• based on low-noise Infineon MMIC BGA614
• mounting option for one (default, positive output) or two MMIC stages (negative output)
• options for preamp voltage supply (+5V): either via separate connector (J2) or remote powering via output signal (default)

Preamplifier schematic

For the different operation modes, the following mounting options are offered (unmentioned components are identical as indicated in the schematic or as in the default option):

Default (single-stage, remote powering)

• do not mount: IC2, C5, C6, L4, R5, C7, J2, J5
• mount: R7 (0R), R6 (0R), C2 (0R), connect IC2 pins 1 to 3 (e.g. with edge mounted 0R resistor)

Dual-stage

• mount: IC2, R6/C7 = pole-zero-cancellation network (e.g. 47R/22p)

Separate power supply connection

• do not mount: L3
• mount: J2

Floating bias voltage supply (galvanically isolated from signal GND)

• dnm: R7
• mount C5, C6

General purpose 50Ω RF amplifier (no SiPM, signal input via u.Fl socket J5)

• dnm: J1, J3, R1, R2, L2
• mount: J5

mounted preamp (top) and photosensor PCBs (bottom) with one instrumented SiPM

Mounted preamp plugged on the pin headers of the SiPM board of an assembled detector plate