Amplifier

Introduction to Amplifier

A device that adds signal amplitude or power, which is an important element of signal processing in automated technology tools. The amplification of the amplifier is achieved by controlling the energy from the input signal. The power required for amplification is provided by the energy source. For a linear amplifier, the output is the reproduction and enhancement of the input signal. For nonlinear amplifiers, the output is a function of the input signal. The amplifiers are classified into mechanical amplifiers, electromechanical amplifiers, electronic amplifiers, hydraulic actuators, and pneumatic amplifiers according to the physical quantities of signals processed, among which the most widely used are electronic amplifiers. With the advent of jet technology (see fluidic components), the use of hydraulic or pneumatic amplifiers has also increased. Electronic amplifiers are also divided into vacuum tube amplifiers, transistor amplifiers, solid state amplifiers, and magnetic amplifiers according to the active devices used, among which transistor amplifiers are most widely used. In automated meters, transistor amplifiers are commonly used for voltage amplification and current amplification of signals. The main forms are single-ended amplification and push-pull amplification. In addition, it is often used for impedance matching, isolation, current-voltage conversion, charge-voltage conversion (such as the charge amplifier) ​​and the use of amplifiers to achieve a certain functional relationship between the output and input (such as operational amplifiers).

The role of the amplifier

1. A device capable of amplifying the voltage or power of an input signal, consisting of an electron tube or transistor, a power transformer, and other electrical components. Used in communications, radio, radar, television, automatic control and other devices.

Principle: The high-frequency power amplifier is used in the final stage of the transmitter. The function is to amplify the high-frequency modulated signal to meet the requirements of the transmission power. Then the antenna is radiated to the space to ensure the reception in a certain area. The machine can receive a satisfactory signal level and does not interfere with the communication of adjacent channels.

High-frequency power amplifiers are important components of transmission devices in communication systems. According to the width of its operating frequency band is divided into narrow-band high-frequency power amplifier and broadband high-frequency power amplifier of the two, narrow-band high-frequency power amplifier usually has a frequency-selective filtering of the frequency-selection circuit as an output loop, it is also known as tuning power amplifier or Resonant power amplifier; The output circuit of the wideband high frequency power amplifier is a transmission line transformer or other wideband matching circuit, so it is also called an untuned power amplifier. A high frequency power amplifier is an energy conversion device. It converts the DC energy supplied by the power supply into high frequency AC output. It is known in the course of “low frequency electronic circuit”. The amplifier can be divided into A according to the current conduction angle. Class B, C, and C work states. Class A amplifier current flow angle of 360o, suitable for small-signal low-power amplification. Class B amplifier current flow angle is equal to about 180o; Class C amplifier current flow angle is less than 180o. Both Types B and C are suitable for high power operation Class C. The output power and efficiency are the highest of the three operating states. Most high frequency power amplifiers work in Class C. However, the current waveform of Class C amplifiers is too distorted and therefore cannot be used for low-frequency power amplification. It can only be used for resonant power amplification using a tuned loop as a load. Due to the filtering ability of the tuning loop, the loop current and voltage are still very close to the sinusoidal waveform and the distortion is small.

2. When drawing, zoom in or out of the graphics appliance. Also called a magnifying scale.

Classification of amplifiers

Integrated Op Amp Main Category

The following describes the integrated op amps with different characteristics.

1. Universal integrated operational amplifier

The general-purpose integrated operational amplifier means that its technical parameters are relatively moderate and can meet the requirements for use in most cases. The general-purpose integrated operational amplifier is divided into I type, II type and III type, among which I is a low gain operational amplifier, II is a medium gain operational amplifier, and III is a high gain operational amplifier. Type I and Type II are basically early products with an input offset voltage of about 2 mV and an open-loop gain of more than 80 dB.

2. High-precision integrated operational amplifier

High-precision integrated operational amplifiers are op amps with small offset voltages, very small temperature drift, and very high gain and common-mode rejection ratios. The noise of this type of operational amplifier is also relatively small. Among them, the offset voltage of a single high-precision integrated operational amplifier can be as small as a few microvolts, and the temperature drift is as small as several tens of microvolts per degree Celsius.

3. High-speed integrated operational amplifier

High-speed integrated operational amplifiers have large output voltage conversion rates, some as high as 2 to 3 kV/μS.

4. High input impedance integrated operational amplifier

The high input impedance integrated op amp has a very large input impedance and very low input current. The input stage of this type of operational amplifier often uses MOS transistors.

5. Low power integrated operational amplifier

Low-power integrated op amps operate with very low currents and low supply voltages. The entire op amp consumes only tens of microwatts. This type of integrated operational amplifier is mostly used in portable electronic products.

6. Broadband integrated operational amplifier

Broadband integrated operational amplifiers have a wide frequency band, with a unity-gain bandwidth of more than gigahertz, and are often used in wide-band amplifier circuits.

7. High-voltage integrated operational amplifier

The supply voltage of the general integrated operational amplifier is below 15V, and the supply voltage of the high voltage integrated operational amplifier can reach several tens of volts.

8. Power type integrated operational amplifier

The output stage of the power type integrated operational amplifier can provide relatively large power output to the load.

9. Fiber Amplifier

Optical fiber amplifier can not only directly amplify the optical signal, but also has real-time, high-gain, wide-band, on-line, low-noise, low-loss full-optical amplification function, and is an indispensable key device in a new generation of optical fiber communication systems. This technology not only solves the limitation of attenuation on the transmission rate and distance of the optical network, but more importantly, it creates a wavelength division multiplex of the 1550 nm frequency band, which will enable ultra-high speed, large capacity, and ultra-long distance wavelength division multiplexing (WDM). ), Dense Wavelength Division Multiplexing (DWDM), all-optical transmission, and optical soliton transmission have become a reality. It is an epoch-making milestone in the history of optical fiber communications. In current practical optical fiber amplifiers, there are mainly erbium doped fiber amplifiers (EDFA), semiconductor optical amplifiers (SOA), and fiber-optic Raman amplifiers (FRA), among which erbium doped fiber amplifiers have been widely used for their superior performance. Distance, high-capacity, high-rate optical fiber communication systems, access networks, fiber CATV networks, military systems (radar multiplex data multiplexing, data transmission, guidance, etc.) and other fields, as power amplifiers, relay amplifiers, and preamplifiers .

Fiber amplifiers generally consist of a gain medium, pump light, and input-output coupling structures. At present, there are mainly three types of fiber amplifiers, ie, Erbium doped fiber amplifiers, semiconductor optical amplifiers and fiber Raman amplifiers. According to their application in optical fiber networks, optical fiber amplifiers mainly have three different uses: they are used as power amplifiers on the transmitter side to improve emission. Machine power; pre-amplifier before the receiver to greatly improve the sensitivity of the optical receiver; in the optical transmission line as a repeater amplifier to compensate for optical fiber transmission loss, to extend the transmission distance.