1. What is Common Emitter Voltage Gain?

The common emitter voltage gain is a key parameter in BJT (Bipolar Junction Transistor) amplifier circuits that describes the amplification factor of the input signal. It represents the ratio of output voltage to input voltage in a common emitter configuration.

2. How Does the Calculator Work?

The calculator uses the common emitter voltage gain formula:

Where:

• \( A_v \) — Voltage gain (unitless)
• \( R_C \) — Collector resistance (Ω)
• \( r_e \) — Emitter resistance (Ω)

Explanation: The negative sign indicates a 180-degree phase shift between input and output signals, which is characteristic of common emitter amplifiers. The gain is determined by the ratio of collector resistance to emitter resistance.

3. Importance of Voltage Gain Calculation

Details: Accurate voltage gain calculation is crucial for designing amplifier circuits, predicting signal amplification, ensuring proper circuit performance, and avoiding signal distortion in electronic systems.

4. Using the Calculator

Tips: Enter collector resistance (R_C) and emitter resistance (r_e) in ohms (Ω). Both values must be positive and non-zero for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: Why is the voltage gain negative?
A: The negative sign indicates phase inversion - the output signal is 180 degrees out of phase with the input signal, which is a fundamental characteristic of common emitter amplifiers.

Q2: What are typical voltage gain values?
A: Typical voltage gains range from 10 to 200 for common emitter amplifiers, depending on the specific circuit design and component values used.

Q3: How does temperature affect voltage gain?
A: Temperature changes can affect transistor parameters and resistance values, which may slightly alter the actual voltage gain from calculated values.

Q4: What is the relationship between r_e and transistor current?
A: The emitter resistance r_e is approximately equal to 25mV/I_E, where I_E is the emitter current, making it dependent on the operating point of the transistor.

Q5: When is this simplified formula not accurate?
A: This formula assumes ideal conditions and may not account for effects like Early voltage, parasitic capacitances, or when the amplifier is operating near its frequency limits.