Negative feedback amplifier

Negative feedback amplifier
Original: Brews ohare Vector: Serenthia · CC BY-SA 3.0 · source
Type	Negative feedback amplifier

Negative feedback amplifier. A negative feedback amplifier is an electronic circuit that uses feedback to reduce the gain of an amplifier, increasing its stability and accuracy. This concept was first introduced by Harold Stephen Black, an AT&T engineer, in his work on telecommunications systems, particularly in the development of the transcontinental telephone line. The idea of negative feedback was also explored by Harry Nyquist, who worked on stability theory and its application to control systems, including those used in NASA's Apollo program.

Introduction

The negative feedback amplifier is a fundamental component in electronic engineering, widely used in audio equipment, medical devices, and industrial control systems. The concept of negative feedback was first applied by Karl Ferdinand Braun in his work on cathode ray tubes, and later developed by Guglielmo Marconi in his wireless telegraphy systems. The negative feedback amplifier is also related to the work of Lee de Forest, who invented the audion tube, a precursor to the vacuum tube. Other notable figures, such as John Ambrose Fleming and Irving Langmuir, contributed to the development of vacuum tubes and their application in amplifier design.

Principles of Operation

The negative feedback amplifier operates by feeding a portion of the output signal back to the input, but with the opposite phase. This feedback signal is then combined with the input signal, reducing the overall gain of the amplifier. The amount of feedback is determined by the feedback ratio, which is the ratio of the feedback signal to the output signal. The negative feedback amplifier is commonly used in operational amplifiers, which are a fundamental component in analog computers and signal processing systems, including those used in MIT's Laboratory for Computer Science and Stanford University's Department of Electrical Engineering. The work of Claude Shannon on information theory also laid the foundation for the development of modern communication systems, which rely heavily on negative feedback amplifiers.

Types of Negative Feedback

There are several types of negative feedback, including voltage feedback, current feedback, and power feedback. Voltage feedback is the most common type, where a portion of the output voltage is fed back to the input. Current feedback is used in power amplifiers, where a portion of the output current is fed back to the input. Power feedback is used in high-power amplifiers, where a portion of the output power is fed back to the input. The work of Nikola Tesla on alternating current systems and George Westinghouse on polyphase systems also contributed to the development of modern power systems, which rely on negative feedback amplifiers. Other notable figures, such as Charles Proteus Steinmetz and Oliver Heaviside, worked on the development of electrical engineering and telecommunications systems.

Stability and Oscillation

The negative feedback amplifier can become unstable and oscillate if the feedback loop gain is too high. This is because the feedback signal can become larger than the input signal, causing the amplifier to oscillate. The stability of the amplifier can be analyzed using Nyquist stability criterion, which was developed by Harry Nyquist. The work of Bode on control theory also contributed to the understanding of stability and oscillation in negative feedback amplifiers. The IEEE and IET have published numerous papers on the stability and oscillation of negative feedback amplifiers, including those used in space exploration and medical imaging.

Applications and Examples

Negative feedback amplifiers are widely used in audio equipment, such as guitar amplifiers and public address systems. They are also used in medical devices, such as electrocardiogram machines and ultrasound machines. In industrial control systems, negative feedback amplifiers are used to control temperature, pressure, and flow rate. The work of Norbert Wiener on cybernetics and control theory also laid the foundation for the development of modern control systems, which rely heavily on negative feedback amplifiers. Other notable applications include NASA's Space Shuttle program and CERN's Large Hadron Collider.

Analysis and Design

The analysis and design of negative feedback amplifiers involve the use of circuit analysis and control theory. The transfer function of the amplifier is used to analyze the stability and frequency response of the amplifier. The gain margin and phase margin are used to determine the stability of the amplifier. The work of Laplace on transform theory and Fourier on analysis also contributed to the development of modern signal processing and control systems, which are used to analyze and design negative feedback amplifiers. The University of California, Berkeley and Massachusetts Institute of Technology have developed numerous courses and programs on the analysis and design of negative feedback amplifiers, including those used in robotics and autonomous systems. Category:Electronic components