[Actual] Difference Between Power Amplifier and Voltage Amplifier

The main difference between a Power amplifier and a Voltage amplifier is, Power Amplifier low output impedance but a voltage amplifier has high output impedance.

Power Amplifiers and Voltage amplifiers both are very useful and they are used for different purposes. Here you will find the important differences between the Power Amplifier and Voltage Amplifier.

Power Amplifier VS Voltage Amplifier

Power Amplifier	Voltage Amplifier
The power amplifier amplifies the power of a signal.	A voltage amplifier amplifies the voltage or increases the voltage level of a signal.
The input signal of the power amplifier must have a high magnitude.	The voltage amplifier can work with a low-magnitude signal.
The current gain of the power amplifier is very high, it greater than 100	The current gain of the voltage amplifier is very low, it lies between 5 to 20
Transformer coupling is used in Power Amplifier.	RC coupling is used in Voltage amplifiers.
The transistor used in the Power Amplifier has a thick base because it handles a very large current.	The transistor used in the voltage amplifier has a thin base because it does not handle large currents, it just increases the voltage level of the input signal
The output impedance of the power amplifier is very low, up to 200ohm	The output impedance of the voltage amplifier is very high, about 12 kilo-ohm

Other Differences between the Voltage Amplifier and Power Amplifier

1. The collector current of the voltage amplifier is very low up to 1 mA but the collector current of the power amplifier is high greater than 100 mA

2. The voltage amplifier is used for small signal voltage, but the power amplifier is used for comparatively high voltage signals.

3. The collector resistance of the voltage amplifier is high but the collector resistance of the power amplifier is high.

4. Generally, the voltage amplifier is used for the amplification of a very low voltage signal in a circuit, whereas the power amplifiers are used for driving the loudspeaker.

5. Common Applications of Power Amplifiers are Audio Systems, Radio Frequency (RF) Communication, Instrumentation and Measurement, and Medical Devices(ultrasound machines, ECG monitors). On the other hand common applications of voltage amplifiers are Signal Conditioning, Instrumentation, Audio Pre-Amplification, Feedback Systems, Analog to Digital Conversion, Equalizers and Tone Controlling circuits, etc.

A voltage amplifier increases the voltage level of a signal whereas the power amplifier increases the power of the signal. It is an important difference between the power amplifier and the voltage amplifier.

As the voltage amplifier has a high output impedance, so low impedance load cannot be connected to it, because it could not be delivered high load current. On the other hand, the power amplifier has low output impedance so it can deliver a high current.

For the above two reasons, in the Audio system, at first audio signal coming from the microphone is converted into an electrical signal. This electrical signal gives to the voltage amplifier which increases the voltage level of the signal. then the output signal from the voltage amplifier is fed to the power amplifier. The power amplifier increases the power of the signal to drive a loudspeaker.

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