Question
Download Solution PDFThe peak power dissipated per transistor in case of a class B push-pull power amplifier if Vcc = 15 V and
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFPeak Power Dissipated in a Class B Push-Pull Power Amplifier
Problem Statement: In the given question, we are tasked with calculating the peak power dissipated per transistor in a Class B push-pull power amplifier. The circuit parameters are:
- Supply Voltage (
VCC VCC ) = 15 V - Load Resistance (
R′L RL′ ) = 5 Ω
Class B Push-Pull Amplifier Basics:
A Class B push-pull amplifier operates with each transistor conducting for half of the input signal cycle (180°). The transistors work in complementary pairs, ensuring the output waveform is continuous and distortion-free. The maximum power dissipation in a Class B amplifier occurs when the output signal is at its peak value.
The power dissipated in a transistor depends on the supply voltage, load resistance, and the characteristics of the output waveform. The relevant formulas for this calculation are derived from the principles of power dissipation in amplifiers.
Key Formulas:
- The peak current through the load is given by:
IL(peak)=VCCR′L IL(peak)=VCCRL′ - The RMS current through the load is:
IL(rms)=IL(peak)2–√=VCC2–√⋅R′L IL(rms)=IL(peak)2=VCC2⋅RL′ - The RMS power dissipated across the load is:
PL=I2L(rms)⋅R′L=(VCC2√⋅R′L)2⋅R′L1 PL=IL(rms)2⋅RL′=(VCC2⋅RL′)2⋅RL′1 - The peak power dissipated per transistor is:
Ptransistor(peak)=V2CCπ2⋅R′L Ptransistor(peak)=VCC2π2⋅RL′
Calculation:
- First, substitute
VCC=15V VCC=15V andR′L=5Ω RL′=5Ω into the formula for peak power dissipation:Ptransistor(peak)=V2CCπ2⋅R′L Ptransistor(peak)=VCC2π2⋅RL′ - Now calculate
V2CC VCC2 :V2CC=152=225 VCC2=152=225 - Substitute
V2CC=225 VCC2=225 andR′L=5 RL′=5 into the equation:Ptransistor(peak)=225π2⋅5 Ptransistor(peak)=225π2⋅5 - Simplify:
Ptransistor(peak)=2255⋅π2=45π2 Ptransistor(peak)=2255⋅π2=45π2
Answer: The peak power dissipated per transistor is
Important Information:
Let’s analyze why other options are incorrect:
Option 2:
This is incorrect because it does not match the formula derived for the peak power dissipation. The presence of
Option 3:
This option is incorrect because the numerator (90) does not align with the actual computation. The correct numerator is 45, as derived in the solution.
Option 4:
Although the numerator is correct, the denominator does not include
Conclusion:
The peak power dissipation in a Class B push-pull power amplifier occurs when the output signal reaches its maximum value. This power is calculated using the relationship
Last updated on Jul 15, 2025
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