Question 7.7: The following readings were obtained experimentally from a J...

(a) From the given readings we find that with constant V_{Gs} at OV,

∂  V_{DS} = 15 -7 = 8 V

∂  I _{D} = 10.25 -10 = 0.25 mA.

So, ac drain resistance,          r_{d}=\left . \frac{∂ V_{DS}}{∂  I_{D}} \right | const. V_{GS}

=\frac{8 V}{0.25  mA}=32  KΩ

(b) Again from the readings it is seen that with V_{DS} constant at 15 V,

∂  V_{GS} = 0.2 -0 = 0.2 V
∂  I_{D} = 10.25-9.65 = 0.6 mA.

So, transconductance,              g_{m}=\left . \frac{∂ I_{D} }{∂ V_{GS} } \right | const V_{DS}

Or,                                                g_{m}=\frac{0.6  mA}{0.2  V}

= 3000 µ mho

(c) Amplification factor, µ = g_{m} ×r _{d}

= (3000×10^{–6}) (32×10^{3} )

Or,                                         µ = 96.