Comparison of Fast Response and Noise of Charge-Sensitive Amplifiers with Various Types of Input Fets

The circuit simulation results of the charge-sensitive amplifiers (CSA) with various types of input field-effect transistors (FET) are considered. CSA-1 and CSA-2 are implemented on Si bipolar transistors, besides in CSA-1 the input transistor is a Si field-effect transistor with p-n junction (Junction Field Effect Transistor, JFET) and in CSA-2 - a GaAs FET with a gate formed by Schottky contact (metalized semiconductor FET, MESFET). CSA-3 is developed completely on the GaAs MESFET. In order to adequately compare the CSAs with respect to the rise-time τ of the output pulses and the equivalent noise charge (ENC), all input transistors were selected with approximately equal drain current and the ratio of the gate width to the length W/L. The electrical circuits of the CSAs, the simulation results of the operating mode, the critical parameters, the dependence of τ and the ENC on the capacity of the input signal source C
_D
are presented.