Page 3 - Transistor and FET New

11. FET resembles what?

Ans: FET resemble that of a pentode valve.

12. Name the FET parameters
(i) a.c. drain resistance (rd).
It is the ratio of change in drain-source voltage (ΔVDS) to the change in drain
current (ΔID) at constant gate-source voltage i.e.

a.c. drain resistance, rd = ΔVDS/ ΔID at constant VGS

(ii) Transconductance ( gfs). It may be defined as follows :
It is the ratio of change in drain current (ΔID) to the change in gate-source voltage
(ΔVGS) at constant drain-source voltage

i.e. Transconductance, gfs = ΔID / ΔVGS at constant VDS

(iii) Amplification factor ( µ ).
It is the ratio of change in drain-source voltage ( ΔVDS) to the change in gate-
source voltage (ΔVGS) at constant drain current i.e.
Amplification factor, µ = ΔVDS / ΔVGS at constant ID

13. What is MOSFET? List the types.
Ans: MOSFET:A field effect transistor (FET) that can be operated in the
enhancement-mode is called a MOSFET.
Types: 1. Depletion-type MOSFET or D-MOSFET
2. Enhancement-type MOSFET or E-MOSFET

14.Why MOSFET is also called IGFET?
Ans:
The SiO2 layer is an insulator. The gate terminal is made of a metal conductor.

Thus, going from gate to substrate, there is a metal oxide semiconductor and
hence the name MOSFET.
Since the gate is insulated from the channel, the MOSFET is sometimes called

insulated-gate FET (IGFET). However, this term is rarely used in place of the term
MOSFET.

Dr P I Mandi, Dept. of Electronics , Basaveshwar Science College,Bagalkot # 2019 -20