A voltage amplifier is an electronic circuit or device designed to increase the amplitude of an input voltage signal. It's commonly used in various applications, such as audio systems, communication systems, and instrumentation, where the original signal needs to be boosted without significant distortion.
Voltage amplification is achieved through the use of active components like transistors or operational amplifiers (op-amps) in combination with passive components like resistors, capacitors, and sometimes inductors. The basic principle behind how a voltage amplifier works involves using the active component to control the flow of current through the circuit, which results in a larger output voltage compared to the input.
Here's a simplified explanation of how a common transistor-based voltage amplifier works:
Biasing: The input voltage signal is applied to the base terminal of a transistor (typically a bipolar junction transistor or BJT). The base-emitter junction is forward-biased using a suitable biasing circuit, which sets the transistor in an active region.
Amplification: As the input voltage varies, it causes corresponding variations in the base current of the transistor. The transistor's current gain (β) causes a much larger collector current to flow. This collector current flows through a collector resistor, creating a voltage drop across it.
Output Stage: The voltage drop across the collector resistor results in an amplified output voltage across the collector terminal of the transistor. This amplified output voltage is taken from the collector terminal and is usually the amplified version of the input signal.
By controlling the base current using the input signal, the transistor effectively acts as a current amplifier. The amplified current flowing through the collector resistor results in a larger output voltage. The degree of amplification is determined by the transistor's characteristics, the biasing conditions, and the values of the surrounding circuit components.
Operational amplifiers (op-amps) are another commonly used component in voltage amplification circuits. Op-amps are integrated circuits designed to have extremely high gain and excellent linearity. They can be used in various configurations, such as inverting amplifiers, non-inverting amplifiers, and differential amplifiers, to achieve different levels of voltage amplification.
In summary, a voltage amplifier boosts the amplitude of an input voltage signal by using active components like transistors or op-amps to control the flow of current through the circuit, resulting in a larger output voltage that's proportional to the input signal.