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Rohit Chatterjee · 12th October 2009, 06:34 PM

Can a depletion-MOSFET be operated as an enhancement-MOSFET???Or vice versa???Please xplain.....

smanches · 12th October 2009, 07:15 PM

Sure. The only difference is that a depletion mode turns off with power to the gate, while an enhancement mod turns on with power to the gate.

If you want to use a depletion as an enhancement, you'll need to keep power to the gate always to keep it off, then take the power way to turn it on. And the opposite with an enhancement mode mosfet.

Rohit Chatterjee · 13th October 2009, 06:18 PM

I dont get it exactly....Consider the case of a n-channel MOSFET....
If its a depletion MOSFET,it is ON for V_GS=0...As V_GS is decreased the n channel gets depleted and beyond the threshold voltage the MOSFET turns OFF....On the other hand if V_GS>0, electrons from the bulk are enter the conducting channel and increase the conductivity,thus ensuring enhancement mode operation....
Now if its an enhancement MOSFET,if V_GS is greater than the thermal voltage,a conducting channel(inversion layer) is formed and the device is ON....But how can this MOSFET operate in the depletion mode????There is simply no conducting channel which can be depleted for V_GS<0....

crutschow · 13th October 2009, 07:18 PM

That is correct. Enhancement-mode and depletion-mode transistors operate by a different mechanism and are not interchangeable.

ronsimpson · 13th October 2009, 07:21 PM

semisouth.com has some information on power jfets.
http://semisouth.com/products/upload...3_rev1.3.1.pdf (data sheet for SJEP1206R063)

Some MOSFETS have both the insulated and the junction gate available.

Rohit Chatterjee · 13th October 2009, 07:21 PM

Well m gettin a bit confused ovr here....a depletion MOSFET can be operated as an enhancement MOSFET......but the reverse isnt true....ryt????

smanches · 13th October 2009, 08:54 PM

So was I totally wrong and talking out my non-coffeed a$$ again?

EDIT: So could a dep-mode PNP be used like a enh-mode NPN?

EDIT2: nvm, answered my own dumb question.

weglobal · 21st October 2009, 04:52 AM

Hi
I need a help to design a battery charger from solar panel , I have a 6V 2.2W solar panel which I am connecting to a 3.6V NIMH 2500mAh battery, I want to use a MOSFET as switch so I will be monitoring the bat voltage , when rich 4.5V the MOSFET will be turned OFF , the reason also that I am using the MOSFET is to not have too much losses and also for power of thr battery not to come back to the solar once the MOSFET is OFF and solar voltage is lower than the Battery.

smanches · 21st October 2009, 02:06 PM

do not cross post please, and do not hijack other peoples threads.

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12th October 2009, 06:34 PM	#1
Rohit Chatterjee	Mosfet... Can a depletion-MOSFET be operated as an enhancement-MOSFET???Or vice versa???Please xplain..... Last edited by Rohit Chatterjee; 12th October 2009 at 06:36 PM.

12th October 2009, 07:15 PM	#2
smanches	Sure. The only difference is that a depletion mode turns off with power to the gate, while an enhancement mod turns on with power to the gate. If you want to use a depletion as an enhancement, you'll need to keep power to the gate always to keep it off, then take the power way to turn it on. And the opposite with an enhancement mode mosfet.

13th October 2009, 06:18 PM	#3
Rohit Chatterjee	I dont get it exactly....Consider the case of a n-channel MOSFET.... If its a depletion MOSFET,it is ON for V_GS=0...As V_GS is decreased the n channel gets depleted and beyond the threshold voltage the MOSFET turns OFF....On the other hand if V_GS>0, electrons from the bulk are enter the conducting channel and increase the conductivity,thus ensuring enhancement mode operation.... Now if its an enhancement MOSFET,if V_GS is greater than the thermal voltage,a conducting channel(inversion layer) is formed and the device is ON....But how can this MOSFET operate in the depletion mode????There is simply no conducting channel which can be depleted for V_GS<0....

13th October 2009, 07:18 PM	#4
crutschow	That is correct. Enhancement-mode and depletion-mode transistors operate by a different mechanism and are not interchangeable. __________________ Carl Curmudgeon Elektroniker

13th October 2009, 07:21 PM	#5
ronsimpson	semisouth.com has some information on power jfets. http://semisouth.com/products/upload...3_rev1.3.1.pdf (data sheet for SJEP1206R063) Some MOSFETS have both the insulated and the junction gate available.

13th October 2009, 08:54 PM	#7
smanches	So was I totally wrong and talking out my non-coffeed a$$ again? EDIT: So could a dep-mode PNP be used like a enh-mode NPN? EDIT2: nvm, answered my own dumb question. Last edited by smanches; 13th October 2009 at 09:57 PM.

21st October 2009, 04:52 AM	#8
weglobal	Hi I need a help to design a battery charger from solar panel , I have a 6V 2.2W solar panel which I am connecting to a 3.6V NIMH 2500mAh battery, I want to use a MOSFET as switch so I will be monitoring the bat voltage , when rich 4.5V the MOSFET will be turned OFF , the reason also that I am using the MOSFET is to not have too much losses and also for power of thr battery not to come back to the solar once the MOSFET is OFF and solar voltage is lower than the Battery.

21st October 2009, 02:06 PM	#9
smanches	do not cross post please, and do not hijack other peoples threads.