-
In regard to idealised class A BJT amplifiers, the following statements are made about their power relations; Given maximum collector dissipation pD max = 20 watts.
(1) In series-fed load Pac = 10 watts
(2) In transformer coupled load Pac = 20 watts
(3) With series-fed load, DC power Pdc = 40 watts
(4) With transformer coupled load, Pdc = 40 watts
Of these, the true statements are:
-
- only 1, 2
- only 1, 3
- only 2, 3
- only 2, 4
Correct Option: C
Given that
PD (max) = 20 watts.
In series fed, η = 25%
| so 0.25 = | ||
| Pi(dc) |
| 0.25 = | ||
| Pi(dc) |
0.25 Pi (dc) = Pi (dc) – 20
or 0.75 Pi (dc) = 20
| or Pi (dc) = | ≈ 27 watts | |
| 0·75 |
η = 50% → In transformer coupled
| so 0.50 = | ||
| Pi(dc) |
| 0.50 = | ||
| Pi(dc) |
| 0.50 = | ||
| Pi(dc) |
or 0.5 Pi (dc) = 20
| or Pi (dc) = | = 40 watts. | |
| 0.5 |
Po (ac) = Pi (dc) – PD (max)
= 40 – 20 = 20 watts.
Hence alternative (C) is the correct choice.
