What Is a Voltage Amplifier?

Voltage Amplifier is a device that increases the signal voltage. For weak signals, multi-stage amplification is commonly used. Cascade methods include direct coupling, resistance-capacitance coupling, and transformer coupling. They require high amplification, flat frequency response, and low distortion. When the load is a resonant circuit or a coupling circuit, it is required to have better amplitude and phase frequency characteristics and higher selectivity in the specified frequency range.

Chinese name: Voltage amplifier
Foreign name: Voltage Amplifier

Features: Sensor output signal is charge
Classification: Amplifier
Advantages: Frequency bandwidth and high sensitivity

Introduction to voltage amplifier

An operational amplifier is a real analog signal amplification circuit. A variable analog quantity (such as an audio signal or a linearly varying DC voltage) is input to its input terminal; an amplitude amplified but waveform is output at the output Identical, undistorted signals (the proportions of the parts of the output signal waveform and the proportions of the parts of the input signal waveform are the same). The so-called "credit" is the output signal is the result of a mathematical operation of the input signal; that is, the output signal is a multiple of the corresponding part of the input signal (as if the voltage amplitude of each part of the output signal Is the product of the various parts of the input part); it seems that the amplitude of the signal is multiplied. In other words, the operational amplifier is an excellent linear amplifier circuit ^[1] .

How voltage amplifiers work

The core of the operational amplifier is a differential amplifier with a constant current source. As a result of the role of the constant current source, the working point of the transistor can be guaranteed as much as possible. It can work in a relatively linear section of the transistor characteristic curve, and uses deep negative feedback to make the entire operation amplified The circuit has a better linear amplification of the signal. In order to ensure a certain gain, an operational amplifier uses a combination of multi-stage DC amplifiers, which is completed on a chip at the time of manufacture and appears as an integrated circuit operational amplifier; it ensures good coupling characteristics and stability. Therefore, operational amplifiers are synonymous with high-quality analog amplifiers ^[1] .

Because the core of the operational amplifier is a differential amplifier, there are two input terminals and one output terminal. The symbol on the circuit diagram, the position of the pin is the same as the voltage comparator; the relationship between the two input terminals and the output is also Name of non-inverting input and inverting input. Both input terminals can input signals (symmetrical differential signals); also, one input terminal can be set as the reference voltage, and one input terminal can input analog signals ^[1] .

Since the operational amplifier can amplify the signal, it is clear that we can use it instead of the voltage comparator for voltage comparison. There are many circuits that use the operational amplifier circuit to complete the voltage comparison circuit. However, the operational amplifier is used as a voltage comparator; its sensitivity and reflection speed are much worse, so it is better not to use it instead, but the voltage comparator must not be used as an operational amplifier. In general circuit schematics, operational amplifiers and voltage comparators, it is difficult to distinguish whether an operational amplifier or a voltage comparator is shown on the drawing from the symbol, and it can only be determined by analyzing the circuit ^[1] .

Composition of voltage amplifier

Operational amplifiers are composed of amplifying elements such as transistors. Amplifying elements such as transistors are nonlinear elements. It is difficult to make a linear amplifier from a nonlinear amplifier device. The composition of the operational amplifier uses a lot of measures to complete the signal basically close to linear amplification. It is widely used in analog electronic circuits, instruments, and analog computers, and can also be connected to different circuit forms. It is widely used. In the early days, it was used in analog computers as adders and multipliers ^[1] .

Voltage amplifier characteristics

The characteristics of the voltage amplifier: (1) the sensor output signal is a charge; (2) is a high-gain amplifier with deep negative feedback, which is essentially a current \ voltage converter; (3) it is not easy to introduce on-site interference signals, and the circuit is subject to the connection cable The effect of the length change is small, almost negligible, and can be used for long-distance transmission amplification of piezoelectric sensors. (4) Effective measurement of static pressure. (5) Frequency bandwidth, high sensitivity, high signal-to-noise ratio, simple structure, reliable operation and light weight.

Voltage Amplifier Voltage Comparator

Voltage comparators have been widely used in various control circuits and protection circuits; especially in modern LCD and plasma flat-screen TVs, they are even more common applications. Protective circuits in switching power supplies, drive circuits, and backlight board circuits are especially common in flat-screen TVs. They play a great role in the safety and protection of circuits, and also bring us a repair. Upgrade; you must understand and master the principle and working method of the voltage comparator to successfully and successfully complete the fault repair. The following briefly introduces some of the necessary knowledge of the voltage comparator ^[1] .

Voltage comparator

The voltage comparator compares the magnitudes of two analog voltages, and determines which one of them is high and which one is low; and the high-level or low-level indicates the comparison result at the output ^[1] .

Since two voltages are compared; and there is an output terminal of the comparison result, then the comparator must have 3 terminals (except for power supply and ground); two input terminals for comparing analog voltages; one that displays the comparison result To the left of the output are two input terminals; one of which is marked with a "+" sign is called a non-inverting input; the one with a "-" sign is called an inverting input; these two terminals are input analog voltages to be compared. On the right is an output, which outputs the result of the comparison ^[1] .

The relationship between the level of the potential between the two input terminals and the level of the output terminal is as follows:

When the voltage at the non-inverting input is higher than the voltage at the inverting input: the output is high.

When the voltage at the non-inverting input is lower than the voltage at the inverting input: the output is low ^[1] .

Comparison of voltage amplifier and voltage comparator

1. Both symbols are the same;

2. The use of the two is different;

3. The voltage amplifier is "analog amplifier" and requires "linear"; the voltage comparator is "comparison switch" and requires "speed" ^[1]