A low-power high-gain transresistance BiCMOS pulse amplifier for capacitive detector readout

A low-power, high-gain amplifier for detector readout is discussed. The amplifier is balanced, fully differential in circuit topology, and symmetrical in layout, making it radiation tolerant and relatively insensitive to varying magnetic fields in the large detector. Before irradiation, the circuit has a measured differential gain of 110 mV/4 fC, an average 10/90% rise time t_10/90% of 19 ns, a noise figure of 433⊕93·(C_t)^1.08 electrons, e^-, and a power consumption of 750 μW. To keep the core amplifier stable, a low-power super-low gain-bandwidth (SL-GBW) amplifier with a small area is used and also discussed. The SL-GBW amplified has a transition frequency f_T of 38 kHz (including the gain stage, A), a power consumption of 150 nW, a phase margin (PM) of ≈70°, an area of 300×36 μm², and a minimum current per transistor of 7 nA, which is far above the leakage current after irradiation. The complete circuit was implemented in the radiation hard SOI-SIMOX BiCMOS-PJFET technology of DMILL