High Stability Nuclear Pulse Amplifier Analysis

Developments in radiation detectors have established a need for maximum amplifier stability. This paper derives detailed design equations for the transistor current feedback amplifier that are necessary for careful gain stability analyses. These expressions clearly define the open loop gain limitations, and they indicate circuit variations which greatly improve the temperature stability. The parameter rd (1/hoe) of the grounded emitter stage is seen to require the greatest attention. It limits open loop gain, but stability of the open loop gain can still be achieved. The design equations are general, and modifications to the basic loop further improve stability, reduce input and output impedances, or enable the use of high impedance input. A four-transistor feedback loop has been tested that has 0.01 ohms input and output impedances, a gain of 50, 15 ns rise time, and a temperature stability of 10 ppm/°C.