Field Effect Transistors for Charge Amplifiers

In this paper the significance of various noise sources in field-effect transistors is discussed. The intrinsic thermal noise of the conducting channel can be reduced by reducing the channel length. A lower limit to the channel length is set by the carrier velocity saturation effects, which are the hot carrier channel noise and the gate leakage current due to impact ionization. Devices with a ratio of the transconductance to the input capacitance of 3 x 109 sec-1 have been made, and a further improvement appears to be possible.