History - field-effect transistor, Electrical Engineering

History - Field-Effect Transistor:

The principle of field-effect transistors was very first patented by Julius Edgar Lilienfeld in the year 1925 and by Oskar Heil in the year 1934, but practical semi-conducting devices (the JFET, junction gate field-effect transistor) was just only developed much later after the transistor effect was seen and described by the team of William Shockley at Bell Labs in the year 1947. The MOSFET (metal-oxide-semiconductor field-effect transistor) that largely superseded the JFET and had a more profound effect on electronic development was very first planned by Dawon Kahng in 1960.

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Figure: Cross section of an n-type MOSFET

All FETs comprises a gate, drain, and source terminal which correspond roughly to the base, collector, and emitter of BJTs. Apart from the JFET, all FETs as well have a fourth terminal called the body, base, bulk, or substrate. This fourth terminal works to bias the transistor into operation; it is seldom to make non-trivial make use of the body terminal in circuit designs, but its existence is significant when setting up the physical layout of an integrated circuit. The size of the gate, length L in the figure, is the distance in between the source and drain. The width is the extension of the transistor, in the figure perpendicular to the cross section. Commonly the width is much larger than as compared to length of the gate. A gate length of 1µm limits the upper frequency to approximately 5 GHz, 0.2µm to approximately 30 GHz.

Posted Date: 1/11/2013 4:47:15 AM | Location : United States







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