The design of a CMOS peak detect and hold circuit for a portable gamma ray spectroscopy system

A new CMOS peak detect and hold (PDH) circuit based on the two stage, CMOS op amp topology has been developed for a portable gamma ray spectroscopy system under development at the Oak Ridge National Laboratory. The PDH circuit detects and holds a semi-Gaussian voltage pulse until it can be processed by the digital electronics. The PDH circuit operates over a dynamic range of greater than 150:1 with a maximum INL of 0.12%. The PDH circuit has a wide bandwidth of 8.1 MHz, a minimum slew rate of 2 V/μs, a droop rate of only 4.5 μV/us, and a power consumption of less than 100 μW. The control circuits required by the PDH circuit to function within the gamma ray spectroscopy system have also been developed and are presented. A review of gamma ray spectroscopy systems is included to set the context for the PDH circuit design. Then the design, analysis, and experimental results for the PDH prototype are presented. The prototype was fabricated in the 1.2 μm AMI process through MOSIS.