Help with circuit analysis including NMOS

Thread Starter

Morten Andersen

Joined Jun 7, 2019
25
Hello there. im sitting with a practice assignment where i have been given some data and some demands for a circuit, but i can't seem to work it out.
it's about deciding the size of resistors in a NMOS circuit. the demand is that VG gate voltage must be equal to VD drain voltage.
the data given is that the drain current is 3mA, VGS is 1,77V and VDD is 10V.

I have tried writing all the things i know down, but cant really get moving from here.upload_2019-9-26_23-20-31.png
 

crutschow

Joined Mar 14, 2008
23,382
The value for VDS is wrong.
How did you get that voltage?

IR1 is the gate current of the MOSFET.
Do you know how much that typically is?
If not, you need to learn more about MOSFETs.
 
Last edited:

Jony130

Joined Feb 17, 2009
4,983
But can you explain to us how in this circuit you can have a Vgs not equal to Vds?
For this circuit given the Vgs = Vds is always true.
 

crutschow

Joined Mar 14, 2008
23,382
I don't get why people on these kind of forums always have to act so good damm arrogant.
Not all the time.
Only after the poster acts pissy.
You did not answer my question.
You didn't originally state "I measured it", you said "the value of vds is messured on a specific MOSFET."
That's not the same thing.

But if you don't like the answers than go elsewhere for your questions. :p
 

ci139

Joined Jul 11, 2016
725
I don't get why people on these kind of forums always have to act so good damm arrogant.
i guess it's . . . kind of natural . . . all over the www
  • work load stress of ones actual daily work
  • + getting "trapped inside the bubble" --or-- "used to forum environment"
  • + so getting confident and "feeling as if at home" --or-- developing standard model of "other participants" :eek: as dummy bugs ,͡♭♃̡✓̵\➤̲
  • ...
  • ? surfing the web drunk at weekend :confused:
(((( stick in to your subject -- as long as you're been talked to the things are right ))))
(((( don't respond to provocations (would just trash the forum space) ))))
 

Thread Starter

Morten Andersen

Joined Jun 7, 2019
25
Not all the time.
Only after the poster acts pissy.
You did not answer my question.
You didn't originally state "I measured it", you said "the value of vds is messured on a specific MOSFET."
That's not the same thing.

But if you don't like the answers than go elsewhere for your questions. :p
Oh but it is the same thing....
 

Thread Starter

Morten Andersen

Joined Jun 7, 2019
25
i guess it's . . . kind of natural . . . all over the www
  • work load stress of ones actual daily work
  • + getting "trapped inside the bubble" --or-- "used to forum environment"
  • + so getting confident and "feeling as if at home" --or-- developing standard model of "other participants" :eek: as dummy bugs ,͡♭♃̡✓̵\➤̲
  • ...
  • ? surfing the web drunk at weekend :confused:
(((( stick in to your subject -- as long as you're been talked to the things are right ))))
(((( don't respond to provocations (would just trash the forum space) ))))
sounds plausible. if people are gonna help, why not due it in a positive manner..
 

ci139

Joined Jul 11, 2016
725
would you list your values for the resistors RD & R1 -- it's because if they're big it might affect the measurement
e.g. if you put the Voltmeter from gate to GND you shunt it down that closes the channel a bit resulting at a higher reading for Vgs than for Vds
 
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