Class B Power Amplifier Efficiency Calculation

Class B Power Amplifier Efficiency Formula:

\[ \eta = \frac{\pi}{4} \times 100\% \approx 78.5\% \]

Calculated Efficiency:

Maximum Theoretical Efficiency:

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1. What is Class B Power Amplifier Efficiency?

Class B power amplifier efficiency refers to the ratio of AC output power to DC input power, expressed as a percentage. The maximum theoretical efficiency for a Class B amplifier is approximately 78.5%, which is significantly higher than Class A amplifiers.

2. How Does the Calculator Work?

The calculator uses the efficiency formula:

\[ \eta = \frac{P_{out(ac)}}{P_{in(dc)}} \times 100\% \]

Where:

\( \eta \) — Efficiency (%)
\( P_{out(ac)} \) — AC output power (W)
\( P_{in(dc)} \) — DC input power (W)

Maximum Theoretical Efficiency: For ideal Class B amplifiers, the maximum efficiency is \( \frac{\pi}{4} \times 100\% \approx 78.5\% \)

3. Importance of Efficiency Calculation

Details: Efficiency calculation is crucial for power amplifier design as it determines power consumption, heat dissipation requirements, and overall system performance. Higher efficiency means less power wasted as heat.

4. Using the Calculator

Tips: Enter both DC input power and AC output power in watts. Both values must be positive numbers. The calculator will compute the actual efficiency and show the maximum theoretical efficiency for comparison.

5. Frequently Asked Questions (FAQ)

Q1: Why is Class B amplifier efficiency higher than Class A?
A: Class B amplifiers only conduct current for half of the input cycle, reducing DC power consumption and increasing efficiency compared to Class A amplifiers that conduct continuously.

Q2: What factors affect actual efficiency?
A: Transistor saturation voltage, crossover distortion, component losses, and load impedance mismatch can reduce actual efficiency below the theoretical maximum.

Q3: When is 78.5% efficiency achieved?
A: The maximum efficiency of 78.5% is achieved under ideal conditions with zero saturation voltage and perfect sinusoidal signals at maximum output swing.

Q4: How does efficiency vary with output power?
A: Efficiency increases with output power, reaching maximum at peak output. At lower output levels, efficiency decreases significantly.

Q5: What are practical efficiency values?
A: Practical Class B amplifiers typically achieve 60-70% efficiency due to various losses and non-ideal components.