# Could you help me solve this question? ( Mix of BJT and MOSFET )

#### Hasan Can Ayhan

Feb 18, 2018
1
I have to do this homework for electronics I course. Could you help?

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#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,505
How far have you gotten so far?

What sort of gain are you trying to measure?

If you're completely stumped, do you know how to calculate the gain of the stage containing Q3?

#### Roopa

Feb 22, 2018
1
I have to do this homework for electronics I course. Could you help?

For DC operating point,
As drain current of MOS >> base current of Q2, if we apply KCL at drain node current through R(D1) appoximately equals I(D).
To find V(GS), find V(G) by thevinin's theorem and V(S) by I(S) [remember I(S)=I(D). Substitute in I(D) formulae find I(D)). From that find V(DS)
V(D)=V(B2)==> find V(C2) accordingly find I(C2)
I(C2)=I(E2)==> find V(E2) ==> V(B3) ==> v(E3) ==> V(CE3)

From DC current you find g(m) for small signal analysis.
Draw small signal equivalent and by using KVL and KCL try to find i/p and o/p resistance and overall gain.

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