Analog electronics circuits miscellaneous
- Single stage transformer coupled class A amplifier is delivering the a.c. power to the load of 1.25 watts. The d.c. power from the d.c. supply is:
-
View Hint View Answer Discuss in Forum
NA
Correct Option: B
NA
- Single stage transformer coupled class A power amplifier uses a transistor with maximum dissipation capability of 2.5 watts. The maximum a.c. power in the load is:
-
View Hint View Answer Discuss in Forum
In class A transformer coupled
η = 0·5 = Po(ac) Pi(dc)
where,
Po(ac) → maximum ac power in the load
Pi(dc) → maximum applied dc power to the amplifier
given that PD (max) = 2.50.5 = Po(ac) PD(max) + Po(ac) 0.5 = Po(ac) 2.5 + Po(ac)
1.25 + 0.5 Po (ac) = Po (ac)
0.5 Po (ac) = 1.25or Po (ac) = 1·25 = 2.5 watts. ·5 Correct Option: B
In class A transformer coupled
η = 0·5 = Po(ac) Pi(dc)
where,
Po(ac) → maximum ac power in the load
Pi(dc) → maximum applied dc power to the amplifier
given that PD (max) = 2.50.5 = Po(ac) PD(max) + Po(ac) 0.5 = Po(ac) 2.5 + Po(ac)
1.25 + 0.5 Po (ac) = Po (ac)
0.5 Po (ac) = 1.25or Po (ac) = 1·25 = 2.5 watts. ·5
- In a class A series fed amplifier using a transistor, under conditions the maximum ac power delivered is 1 watt.
The maximum transistor dissipation capability should be:
-
View Hint View Answer Discuss in Forum
Given Po(ac) max = 1 watt
PD (max) =?Again 0.5 = η = Po(ac) Pi(dc) or 0.5 = Po(ac) PD(max) + Po(ac) or 0.5 = 1 PD(max) + 1
or 0.5 PD (max) + 0.5 = 1
or 0.5 PD (max) = 0.5
or PD (max) = 1
Hence alternative (A) is the correct choice.Correct Option: A
Given Po(ac) max = 1 watt
PD (max) =?Again 0.5 = η = Po(ac) Pi(dc) or 0.5 = Po(ac) PD(max) + Po(ac) or 0.5 = 1 PD(max) + 1
or 0.5 PD (max) + 0.5 = 1
or 0.5 PD (max) = 0.5
or PD (max) = 1
Hence alternative (A) is the correct choice.
- In class A direct coupled (series fed) power amplifier, maximum dissipation capability of the transistor is 2.5 watts, when delivering maximum a.c. power in the load is:
-
View Hint View Answer Discuss in Forum
Given PD Max = 2.5 Watts
Poac =?
We know maximum efficiency of direct coupled class-A amplifier is 50% i.e., η = 50%η = 50% = 0.5 = Po(ac) Pi(dc)
∴ Pi (dc) = Po (ac) + PD) Pi (dc)
= Po (ac) + 2.5or 0.5 = Po(ac) Po(ac) + 2·5
or 0.5Po(ac) + 1.25 = Po (ac)
or 0.5 Po (ac) = 1.25or Po (ac) = 1·25 = 2.5 watts. 0·5
where, Po (ac) = output ac power to the load
Pi (dc) = input dc power to the transistorCorrect Option: B
Given PD Max = 2.5 Watts
Poac =?
We know maximum efficiency of direct coupled class-A amplifier is 50% i.e., η = 50%η = 50% = 0.5 = Po(ac) Pi(dc)
∴ Pi (dc) = Po (ac) + PD) Pi (dc)
= Po (ac) + 2.5or 0.5 = Po(ac) Po(ac) + 2·5
or 0.5Po(ac) + 1.25 = Po (ac)
or 0.5 Po (ac) = 1.25or Po (ac) = 1·25 = 2.5 watts. 0·5
where, Po (ac) = output ac power to the load
Pi (dc) = input dc power to the transistor
- For the resonant circuit shown, w0 = 105, Q = 50, R = 400Ω. The value of C is given by:
-
View Hint View Answer Discuss in Forum
Q = ω0L R 50 = 105·L 400
L = 0.2Also ω01 = 1 √LC or ω02 = 1 or C = 1 = 1 LC ω02·L (105)2 × 0·2
= 500 pf
Correct Option: C
Q = ω0L R 50 = 105·L 400
L = 0.2Also ω01 = 1 √LC or ω02 = 1 or C = 1 = 1 LC ω02·L (105)2 × 0·2
= 500 pf