Electronic Devices - FET Amplifiers - Discussion
Discussion Forum : FET Amplifiers - General Questions (Q.No. 41)
41.
Referring to this figure, calculate Zi if rd = 19 k
.
. 
2.42 M
2.50 M
2.53 M
2.59 M
Discussion:
5 comments Page 1 of 1.
Millize said:
4 years ago
Solve for k,
Id = k(Vgs(on)-Vgs(th))^2; k = 0.24 mA/V.
Solve for Vgsq using KVL,
12 - IdRd- Vdsq = 0, substituting Id formula
12 - k(Vgsq-Vgs(th))^2(Rd)-Vdsq =0, but since it is a drain-feedback bias then Vdsq = Vgsq.
Vgsq = 6.41 V.
Solve for gm,
gm = 2k(Vgsq-Vgs(th)) ; gm = 1.64 mS.
Finally solving for Zi = (RF+ rd//RD) / (1+ gm(rd//RD)) since rd<10RD,
Zi = 2.523 M ohms.
Id = k(Vgs(on)-Vgs(th))^2; k = 0.24 mA/V.
Solve for Vgsq using KVL,
12 - IdRd- Vdsq = 0, substituting Id formula
12 - k(Vgsq-Vgs(th))^2(Rd)-Vdsq =0, but since it is a drain-feedback bias then Vdsq = Vgsq.
Vgsq = 6.41 V.
Solve for gm,
gm = 2k(Vgsq-Vgs(th)) ; gm = 1.64 mS.
Finally solving for Zi = (RF+ rd//RD) / (1+ gm(rd//RD)) since rd<10RD,
Zi = 2.523 M ohms.
Markiiee said:
6 years ago
@Ciara.
Where gm comes from? Please explain.
Where gm comes from? Please explain.
Ciara said:
7 years ago
Zi = Rf/(1+gm(rd||Rd)).
gm = 1.64mS.
Rf = 10M ohms.
gm = 1.64mS.
Rf = 10M ohms.
Sellakkannu said:
7 years ago
Please give a clear explanation of the solution.
Rutiksha said:
9 years ago
Please explain the solution.
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