A voltage amplifier is an electronic device that increases the voltage of an input signal while maintaining its shape and characteristics. It is commonly used in audio equipment, communication systems, and various electronic circuits to boost weak signals for further processing or transmission. These amplifiers operate by using a power supply to provide the necessary energy for amplification. The output voltage is typically greater than the input voltage, allowing for improved signal strength. Common types of voltage amplifiers include operational amplifiers and transistor amplifiers, each serving specific applications in electronics.