Other

Siliconix Incorporated

Microwave Technology, Inc.

Neill R Thornton

Adrian I Cogan

J Kirkwood Rough

A BIFET vacuum tube replacement structure includes a plurality of devices that replicate the characteristics of a vacuum tube. The vacuum tube replacement structure has the same pin-out as the vacuum tube being replaced and so can be exchanged directly for a vacuum tube in an audio amplifier. The vacuum tube replacement structure is suitable for use in a wide range of audio amplifier applications without modification to the audio amplifiers. Further, there is no noticeable degradation to the human ear in the sound quality when the vacuum tube replacement structure is used in an audio amplifier in place of a vacuum tube. A unitary device that is a combination of a high impedance bipolar like transistor and a unipolar junction field effect transistor, that is referred to as a BIFET, is used in the vacuum tube replacement structure. In one embodiment, the bipolar like transistor is formed in combination with the gate of the unipolar junction field effect transistor. The vacuum tube replacement structure faithfully replicates input signals at low levels and also slowly and uniformly compresses the input signals at higher drive levels and under overdrive conditions.

BIFET vacuum tube replacement structure

The junction field effect transistors (JFETs) of this invention have improved breakdown voltage capability, reduced on-resistance and improved overdrive capability. The JFET on-resistance is decreased by ion-implanting an insulating layer covering a layer that contains the source and gate regions of the unipolar transistor. The charge of the implanted ions is the same as the charge polarity of the gate regions. To improve the overdrive capability of a JFET a region of conductivity opposite to the conductivity of the gate region is formed in the gate region of the transistor. This region of opposite conductivity creates another junction within the gate region i.e., the junction between the region of opposite conductivity and the gate region, and the junction between the gate region and the layer containing the gate region. The second junction in the gate region of this invention prevents the gate-to-source junction from becoming forward biased until higher gate voltages are applied and thereby provides increased overdrive capability in comparison to prior art JFETs. A new method is used to form a guard ring surrounding the active area of a JFET. The JFET formed using this method has a guard ring of a second conductivity type extending a first distance D1 into a layer having a first conductivity type and a gate region of the second conductivity type extending a second distance D2 into the layer. The method of this invention allows selection of the first and second distances D1, D2 to optimize the breakdown voltage and performance of the JFET of this invention.

High frequency JFET

A trench power MOSFET device is disclosed wherein the method of manufacturing produces a high density MOSFET cell with good breakdown characteristics.

Growing community of inventors

Fremont, CA, United States of America

Neill R Thornton