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Forum: Electrical & Computer Engineering :: Electronics :: MOSFETs  New Topic
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nak31 Problem #52 Mon 5 Oct 2009 9:46:00 PM
Student
Joined Tues 31 Mar 2009
Posts 511

Question 17. In the circuit shown below, VDD is 9 V. The resistor values are RD = 3.3 KΩ, RS = 2.2KΩ, and RG = 470 KΩ.
Find the voltage at the gate of the MOSFET.
Find
VDS (in V) if ID = 1 mA.
Find
ID (in mA) when the MOSFET parameters are k’(W/L) = 1 mA/V and Vt =1.2 V.


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nak31 Tues 6 Oct 2009 11:24:00 AM
Student
Joined Tues 31 Mar 2009
Posts 511

Answer 17.

Since the current entering the gate of a MOSFET is 0, then the valtage at the gate of the MOSFET is 0 V.

2VDD = VRD + VDS + VRS
2*9 = 3.3*1 + VDS + 2.2*1
VDS = 12.5 V.

ID=0.5* kn(W/L)*(VGS - Vt)2, since VGS = VG – VS = 0 – (RsID – VDD)  =VDD -2.2*ID
ID=0.5* 1*( 9-2.2*ID – 1.2)2
Solve to get ID = 2.52 mA.





Nader Kobrosli
Student Rating3.9/5
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