## Q. 4.SP.2

For the MOSFET amplifier of Example 4.5, let $V_{GSQ} = 6.90 \text{V}$. Calculate $I_{DQ}$ from the analog of (4.2) developed in Section 4.8.
$i_{D} = I_{DSS} \left(1 + \frac{v_{GS}}{V_{p0}} \right)^2$        (4.2)

## Verified Solution

From the drain characteristics of Fig. 4-9(b), we see that $V_T = 4 \text{V}$ and that $I_{D\text{on}} = 5 \text{mA}$ at $V_{GSon} = 8 \text{V}$.    Thus,

$I_{DQ} = I_{D\text{on}} \left(1 – \frac{V_{GSQ}}{V_T} \right)^2 = 5 × 10^{-3} \left(1 – \frac{6.90}{4} \right)^2 = 2.63 \text{mA}$

(Compare Example 4.5.)