Question 4.5: In the amplifier of Fig. 4-9(a), VDD = 15 V, RL = 3 kΩ, and ......
In the amplifier of Fig. 4-9(a), V_{DD} = 15 \text{V}, R_L = 3 kΩ, and R_F = 50 MΩ. If the MOSFET drain characteristics are given by Fig. 4-9(b), determine the values of the quiescent quantities.
The dc load line is constructed on Fig. 4-9(b) with v_{DS} intercept of V_{DD} = 15 \text{V} and i_D intercept of V_{DD}/R_L = 5 \text{mA}. With gate current negligible (see Section 4.3), no voltage appears across R_F, and so V_{GS} = V_{DS}. The drain-feedback bias line of Fig. 4-9(b) is the locus of all points for which V_{GS} = V_{DS}. Since the Q point must lie on both the dc load line and the drain-feedback bias line, their intersection is the Q point. From Fig. 4-9(b), I_{DQ} ≈ 2.65 \text{mA} and V_{DSQ} = V_{GSQ} ≈ 6.90 \text{V}.