MODULE 2 JFET, MOSFET AND SCR PREPARED BY: JAYAPRASAD K M ASSISTANT PROFESSOR,EC CEC
JFET ➢The JFET ( ju n ction field -effect tran sistor) is a typ e of FET th at op erates with a reverse-biased pn junction to control current in a channel. HISTORY NOTE ➢ JFET was first patented by Heinrich Welker in 1945. ➢ During 1940s, researchers John Bardeen, Walter Houser Brattain, and William Shockley were trying to build a FET, but failed in their repeated attempts to make a FET. ➢ They discovered the point-contact transistor in the course of trying to diagnose the reasons for their failures. ➢ Following Shockley's theoretical treatment on JFET in 1952 the first working JFET was made in 1953 by George F. Dacey and Ian M. Ross
JFET BASIC STRUCTURE
JFET BASIC OPERATION ➢ Figure shows dc bias voltages applied to an n-channel device. ➢ VDD provides a drain-to-source voltage and supplies current from drain to source. ➢ VGG sets the reverse-bias voltage between the gate and the source ➢ The JFET is always operated with the gate-source pn junction reverse-biased.