TABLE OF CONTENTS We next take a detour from the world of bipolar transistors and enter the world of metal-oxide semiconductor field-effect (MOSFET [1]) transistors. The basic signal MOS gate is discussed, followed by a discussion of MOS amplifiers. The incremental model of the MOS transistor is shown, and it is used in a design example where gain and bandwidth are calculated for a MOS amplifier.
[1] We will not cover the JFET (junction field-effect transistor).
The invention of the metal-oxide semiconductor field-effect transistor (MOSFET) pre-dates the bipolar transistor. An excerpt from one U.S. patent granted in 1933 to Dr. Julius Lilienfeld is shown in Figure 9-1. In three patents, Dr. Lilienfeld gave structures of the MOSFET, MESFET and other MOS devices, but he wasn t able to build any working FETs, underscoring the difficulty in fabricating practical semiconductor devices at that time. In fact, it was not until the 1960s that the first commercially successful FET devices were manufactured.
A basic N-channel lateral MOS gate is shown in Figure 9-2. This is a lateral device because current flow is in the x direction laterally across the surface of the device. [3]
