Electronic Devices - FET Devices - Discussion
Discussion Forum : FET Devices - General Questions (Q.No. 34)
34.
Refer to the following characteristic curve. Calculate the resistance of the FET at VGS = –0.25 V if ro = 10 k
.
. 
1.1378 k
113.78
11.378
11.378 k
Discussion:
6 comments Page 1 of 1.
Katekyo said:
8 years ago
From, Id = Idss(1-Vgs/Vp)^2.
We get, Vp=Vgs/(sqrt(Id/Idss)-1).
Now we know, from the graph, that Idss = 8mA, we jest need to use another curve to get Vp, say, Vgs=-2, Id = 2mA.
Substituting, Vp = (-2)/(sqrt*(2mA/8mA)-1) = -4V.
We get, Vp=Vgs/(sqrt(Id/Idss)-1).
Now we know, from the graph, that Idss = 8mA, we jest need to use another curve to get Vp, say, Vgs=-2, Id = 2mA.
Substituting, Vp = (-2)/(sqrt*(2mA/8mA)-1) = -4V.
(1)
Sanjay said:
9 years ago
Calculation of Vp.
Taking ref of Vgs=0 curve its for max Id = Idss.
So, Vp is point bordering ohmic and a saturation region. Hence its 4v their.
Taking ref of Vgs=0 curve its for max Id = Idss.
So, Vp is point bordering ohmic and a saturation region. Hence its 4v their.
K tuazon said:
9 years ago
How to get vp value?
(2)
K priyanka said:
1 decade ago
How you take vp is -4? Please explain me.
(1)
Priyanka said:
1 decade ago
APPLY FORMULA,
r = ro/(1-vgs/vp)^2 take vp = -4 vgs = -.25 ro given.
10*1000/(1-.25/4)^2.
= 11.378.
r = ro/(1-vgs/vp)^2 take vp = -4 vgs = -.25 ro given.
10*1000/(1-.25/4)^2.
= 11.378.
(1)
Pritam Bhattacharjee said:
1 decade ago
Please explain how do this value occur as an answer.
(1)
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