Question 4.SP.20: Fixed bias can also be utilized for the enhancement-mode MOS......
Fixed bias can also be utilized for the enhancement-mode MOSFET, as is illustrated by the circuit of Fig. 4-25. The MOSFET is described by the drain characteristic of Fig. 4-9. Let R_1 = 60 kΩ, R_2 = 40 kΩ, R_D = 3 kΩ, R_L = 1 kΩ, V_{DD} = 15 \text {V, and} C_C → ∞. (a) Find V_{GSQ}. (b) Graphically determine V_{DSQ} and I_{DQ}.
(a) Assume i_G = 0. Then, by (4.3),
R_G = \frac{R_1R_2}{R_1 + R_2} \quad \text{and} \quad V_{GG} = \frac{R_1}{R_1 + R_2} V_{DD} (4.3)
(b) The dc load line is constructed on Fig. 4-9 with v_{DS} intercept V_{DD} = 15 \text{V} and i_D intercept V_{DD}/R_L = 5 \text{mA}. The Q-point quantities can be read directly from projections back to the i_D and v_{DS} axes; they are V_{D S Q} \approx 11.3 \text{V} and I_{D Q} \approx 1.4 \text{mA}.