In a certain CE amplifier with emitter resistance and emitter by-pass ...
The r
e model of CE transistor.
Therefore, gain will decrease if we remove capacitor.
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In a certain CE amplifier with emitter resistance and emitter by-pass ...
Explanation:
When a capacitor is used to bypass the emitter resistor in a common emitter (CE) amplifier, it provides a low impedance path for the AC signal to bypass the emitter resistor. This effectively reduces the negative feedback provided by the emitter resistor, resulting in a higher voltage gain for the amplifier.
Effect of Bypass Capacitor:
1. Reduction in emitter resistance: The bypass capacitor, when connected in parallel to the emitter resistor, reduces the effective resistance seen by the AC signal. This is because the reactance of the capacitor decreases with increasing frequency, allowing more AC current to flow through it. As a result, the effective emitter resistance decreases.
2. Increased bypass of AC signal: The bypass capacitor provides a low impedance path for the AC signal, allowing it to bypass the emitter resistor. This means that a significant portion of the AC signal does not have to flow through the emitter resistor, reducing the voltage drop across it.
3. Increased AC voltage gain: The voltage gain of a CE amplifier is given by the equation Av = -gm * (Re || RL), where gm is the transconductance of the transistor, Re is the emitter resistor, and RL is the load resistor. When the bypass capacitor is present, the effective emitter resistance (Re || RL) is reduced, leading to a higher voltage gain for the amplifier.
Effect of Removing Bypass Capacitor:
When the bypass capacitor is removed, the AC signal is forced to flow through the emitter resistor. This increases the effective emitter resistance (Re || RL), resulting in a lower voltage gain for the amplifier.
Conclusion:
In conclusion, when the bypass capacitor is removed in a CE amplifier with emitter resistance, the voltage gain of the amplifier decreases. This is because the effective emitter resistance increases, reducing the voltage drop across the emitter resistor and consequently decreasing the voltage gain of the amplifier.