2.10 Common source amplifier

The common source FET circuit shown in Figure 2.10 has the following parameters. Forward transadmittance, y _fs, equals 1.5 10 ^?3 siemens. Output conductance, y _os, equals 10 10 ^?6 siemens. Gate-to-source resistance, r _gs, equals 1 10 ⁸ ohms. Gate-to-drain resistance, r _gd, equals 1 10 ⁸ ohms. Calculate the (a) Z _in, (b) Z _out, and (c) A _v respectively.

Figure 2.10: Common source amplifier

Solution:

r _d = 1/y _os = 1 10 ⁵ ohms

g _m = y _fs = 1.5 10 ^?3

? = y _fsr _d = g _mr _d = 1.5 10 ^?3 1 10 ⁵ = 150

1. Z _in = R _G r _gs = (1 10 ⁶) (1 10 ⁸) = 9.9 10 ⁵ ohms

2. Z _out = R _D rd = R _D 1/y _os = (1 10 ⁴) (1 10 ⁵) = 9,090 ohms

3. A _v = ??[R _D /(r _d + R _D)] = ?(g _mr _d)[R _D/(r _d + R _D)]