A new insulated gate tetrode with high drain breakdown potential and low miller feedback capacitance

Abstract

Insulated gate field effect transistors (IGFET's) with the gate offset from the drain electrode exhibit high drain breakdown potential and very low Miller feedback capacitance. The new insulated gate tetrode (IGT) described in this paper utilizes a second stacked gate to create the offset channel. The main advantage is the possibility of optimizing the device performance, especially the drain breakdown potential for both <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</tex> -and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</tex> -channel devices. Considered in the paper are design and fabrication problems, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V-I</tex> characteristics, drain breakdown potential, dynamic drain resistance, small-signal equivalent circuit, and large-signal limitations. <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</tex> -channel IGT's with drain breakdown potentials up to 300 V have been built. The design of the IGT depends mainly on the tradeoff between drain breakdown potential and the limited frequency response caused by the time constant of the offset channel. The results to date indicate that the IGT has a large drain voltage range and an extremely low Miller feedback capacitance and is adaptable to different operating conditions. The IGT appears very promising for use in power amplifiers and switching applications.