gowri

 Profile 

• Mar 11th, 2009

 

BJT is a current control device where as FET is a voltage control device.

ubabmar

 Profile Answers by ubabmar 

• Jun 24th, 2009

 

1. In BJT because of the current the output will vary.
2. Where as in FET by means of Voltage the output is varied.

Prasannavj

 Profile Answers by Prasannavj 

• Nov 23rd, 2009

 

BJT: Secondary break down occurs.
       Lower Input impedance
       Lower operating frequency
       Higher switching losses
   
FET: PTC for resistance
        No sec break down
        Higher operating frequency
        Higher input impedance
        lower swithing losses

Prasannavj

 Profile Answers by Prasannavj 

• Nov 23rd, 2009

 

BJT as current controlled device -
Base current controls the collector an emitter currents

FET as voltage controlled device-
Field of p or n region decides width of conducting channel in n type or p type FET

hemarajendren

 Profile Answers by hemarajendren 

• Feb 4th, 2011

 

BJT: In bipolar junction transistor, current conduction is only my majority carriers whereas in field effect transistor current conduction is by both majority as well as minority carriers.
Bjt is a current controlled device whereas fet is a voltage controlled device

uzipereg

 Profile Answers by uzipereg 

• Jul 30th, 2011

 

for Active BJT: Ic = BETHA * Ib
(the collector/output current is controlled by the base/input current)

Saturated MOSFET: Id= 0.5*u*Cox*(W/L)*Vod, where Vod is the overdrive voltage: Vod= Vgs - Vt
(the drain/output current is controlled by the overdrive voltage)

swathi

• Apr 9th, 2015

 

In BJT we give input as a current to the base so it operates taking small input current signal and gives large output current signal so it is called current controlled.
in FET we give input voltage signal to the gate so the output will be of current signal so it is called voltage controlled device.