O'Reilly logo

Complete Electronics Self-Teaching Guide with Projects by Harry Kybett, Earl Boyson

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

The JFET as an Amplifier

31 Chapter 3 discussed the JFET in problems 28231, and Chapter 4 discussed the JFET in problems 37241. You may want to review these problems before answering the questions in this problem. Figure 8.30 shows a typical biasing circuit for a JFET.

Questions
A. What type of JFET is depicted in the circuit? _____
B. What value of VGS would you need to turn the JFET completely ON? _____
C. What drain current flows when the JFET is completely ON? _____
D. What value of VGS would you need to turn the JFET completely OFF? _____
E. When a JFET is alternately turned completely ON and OFF in a circuit, what type of component are you using the JFET as? _____
Answers
A. N-channel JFET.
B. VGS = 0 V to turn the JFET completely ON.
C. Drain saturation current (IDSS).
D. VGS should be a negative voltage for the N-channel JFET to turn it completely OFF. The voltage must be larger than or equal to the cutoff voltage.
E. The JFET is being used as a switch.

32 You can use a JFET to amplify AC signals by biasing the JFET with a gate to source voltage about halfway between the ON and OFF states. You can find the drain current that flows in a JFET biased to a particular VGS by using the following equation for the transfer curve:

equation

In this equation, ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required