What Is a Voltage Amplifier?
Voltage amplifiers are devices that amplify the voltage of various electrical signals.
It is also sometimes called a voltage amplifier. A voltage amplifier is a circuit that amplifies an input voltage and outputs it, and is one of the basic components of an electronic device.
Uses of Voltage Amplifiers
Amplifiers are used when a small signal level is input and a larger signal is obtained as output. Since in many cases the input and output signals are voltage signals, devices for this purpose are called voltage amplifiers.
Voltage amplifiers are sold in a variety of forms and with different performance levels, depending on the purpose. The main applications include amplifying audio and video signals, as well as output signals from various sensors.
Principle of Voltage Amplifiers
The circuit configuration of a typical amplifier consists of an amplifying element (transistor, operational amplifier, etc.) and circuits to control it (bias circuit, feedback circuit, etc.). The voltage input to the amplifier element is amplified and output is at a high signal level.
The performance that is important depends on the purpose of use, and suitable circuits are proposed for each of them.
Types of Voltage Amplifiers
There are diverse types of voltage amplifiers on the market. Examples include audio amplifiers, high-frequency amplifiers, and measurement amplifiers.
These commercially available voltage amplifiers have different performance characteristics for various applications. It is important to select the appropriate performance index and use the appropriate voltage amplifiers for the environment in which they will be used.
1. Classification by Frequency
DC Amplifier
DC amplifiers are electronic devices used to amplify and process DC signals. DC amplifiers are used in a variety of applications, including amplification of sensor signals, DC motor control, and power management.
When selecting a DC amplifier, performance requirements, such as input signals, output signals, supply voltage, input impedance, output impedance, and frequency response, should be considered.
Low Frequency Amplifier (Audio Amplifier)
The most typical low-frequency amplifier is an audio amplifier. They are used in speakers, headphones, and other audio equipment to amplify audio signals. Major performance indicators include frequency response, distortion ratio, signal-to-noise ratio, and output power.
High-Frequency Amplifier
High-frequency amplifiers are used to amplify high-frequency signals. Specifically, they are used in wireless communications, satellite communications, and broadcasting. Major performance indicators include frequency bandwidth, gain, noise figure, and input/output impedance.
2. Classification by Function
Measuring Amplifiers
Measurement amplifiers are used to make high-precision measurements. Specifically, they amplify signals from sensors and instruments. Major performance indicators include amplification factor, input/output impedance, linearity, bandwidth, and noise figure.
Low Noise Amplifier
Low noise amplifiers have a low noise figure and are used in sensitive applications. Low noise amplifiers are used to amplify or process weak signals.
When selecting a low noise amplifier, it is important to check performance indicators such as noise figure, voltage gain, bandwidth, input voltage range, and power consumption. Note that low noise amplifiers may be used to reduce noise inside the equipment, and their resistance to noise outside the equipment is not guaranteed.
Differential Amplifier
A differential amplifier has two input terminals and one output terminal. By amplifying the difference between input signals, the effect of noise can be reduced and signal quality can be improved.
Particularly noteworthy performance indicators are PSRR and CMRR. These are very important items in canceling the effects of noise.
High-Voltage Amplifiers
High voltage amplifiers are a type of electronic component used to amplify and process high voltage signals. High voltage amplifiers are used in diverse fields, such as lasers, discharge devices, medical equipment, and industrial equipment.
When selecting high-voltage amplifiers, it is important to check performance indicators, such as output voltage, current, bandwidth, stability, and protection functions. Safety must also be considered, since they handle high voltages.
Other Information on Voltage Amplifiers
1. Characteristics of Voltage Amplifiers
Important indicators of amplifier performance include amplification factor, frequency response, distortion factor, input impedance, and output impedance. These performances are optimized by circuit design according to the intended use and are applicable to various applications.
2. Gain of Voltage Amplifiers
If the input signal of voltage amplifiers is Vin and the output signal is Vout, the gain is expressed as “Vout/Vin times” or “20log (Vout/Vin) dB.”
3. Current Supply Capability
Even voltage amplifiers can supply current to a load up to a certain range. However, voltage characteristics are basically prioritized, and a large current cannot flow, as in the case of power amplifiers.