## Q. 4.7

In the triode amplifier of Fig. 4-14, $V_{GG} = 4 \text{V}, V_{PP} = 300 \text{V}, R_L = 10 kΩ,$ and $R_G = 2 kΩ$. The plate characteristics for the triode are given by Fig. 4-13(b).    (a) Draw the dc load line; then determine the quiescent values (b) $I_{GQ}$,   (c) $V_{GQ}$,   (d) $I_{PQ}$, and (e) $V_{PQ}$.

## Verified Solution

(a)   For the given values, the dc load line (4.11) has the $i_P$ intercept
$i_P = \frac{V_{PP}}{R_L} – \frac{v_P}{R_L}$          (4.11)
$\frac{V_{PP}}{R_L} = \frac{300}{10 × 10^3} = 30 \text{mA}$

and the $v_P$ intercept $V_{PP} = 300 \text{V}$. These intercepts have been utilized to draw the dc load line on the plate characteristics of Fig. 4-13(b).

(b) Since the polarity of $V_{GG}$ is such that $v_G$ is negative, negligible grid current will flow $(I_{GQ} ≈ 0)$.

(c) For negligible grid current, (4.10) evaluated at the $Q$ point yields $V_{GQ} = -V_{GG} = -4 \text{V}$.
$I_{G} = -\frac{V_{GG}}{R_G} – \frac{v_G}{R_G}$          (4.10)

(d) The quiescent plate current is read as the projection of $Q_n$ onto the $i_P$ axis of Fig. 4-13(b) and is $I_{PQ} = 8 \text{mA}$.

(e) Projection of $Q_n$ onto the $v_P$ axis of Fig. 4-13(b) gives $V_{PQ} = 220 \text{V}$.