In the triode amplifier of Fig. 4-14, VGG = 4 V, VPP = 300 V, RL = 10 kΩ, and RG = 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) IGQ, (c) VGQ, (d) IPQ, and (e) VPQ.

Question

In the triode amplifier of Fig. 4-14, [latex]V_{GG} = 4 ext{V}, V_{PP} = 300 ext{V}, R_L = 10 kΩ,[/latex] and [latex]R_G = 2 kΩ[/latex]. 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) [latex]I_{GQ}[/latex], (c) [latex]V_{GQ}[/latex], (d) [latex]I_{PQ}[/latex], and (e) [latex]V_{PQ}[/latex].

Accepted Answer

(a) For the given values, the dc load line (4.11) has the [latex]i_P[/latex] intercept
[latex]i_P = \frac{V_{PP}}{R_L} - \frac{v_P}{R_L}[/latex] (4.11)
[latex]\frac{V_{PP}}{R_L} = \frac{300}{10 × 10^3} = 30 ext{mA}[/latex]

and the [latex]v_P[/latex] intercept [latex]V_{PP} = 300 ext{V}[/latex]. 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 [latex]V_{GG}[/latex] is such that [latex]v_G[/latex] is negative, negligible grid current will flow [latex](I_{GQ} ≈ 0)[/latex].

(c) For negligible grid current, (4.10) evaluated at the [latex]Q[/latex] point yields [latex]V_{GQ} = -V_{GG} = -4 ext{V}[/latex].
[latex]I_{G} = -\frac{V_{GG}}{R_G} - \frac{v_G}{R_G}[/latex] (4.10)

(d) The quiescent plate current is read as the projection of [latex]Q_n[/latex] onto the [latex]i_P[/latex] axis of Fig. 4-13(b) and is [latex]I_{PQ} = 8 ext{mA}[/latex].

(e) Projection of [latex]Q_n[/latex] onto the [latex]v_P[/latex] axis of Fig. 4-13(b) gives [latex]V_{PQ} = 220 ext{V}[/latex].

Chapter 4

Q. 4.7

Q. 4.7

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