 Overview The circuit was designed to create an amplifier that will supply 15 Watts to any load using discrete components.
Terminology - Amplifier – any device that changes, usually increases, the amplitude of a signal
- 2N3055 – a silicon NPN power transistor intended for general purposes
- MJ2955 – the complementary PNP type of 2N3055
Circuit Explanation The 15 Watts power is made possible by using a dual 20 V power supply into a load of 8 ohms. The transistors 2N3055 and MJ2955 are functioning as power transistors because the structure is intended for power switching circuits, series and shunt regulators, output stages and high fidelity amplifiers. The input signal of the circuit, as the Q1 operates in common emitter mode, is delivered to the bias chain of D14, D13, D6, Q9 and Q8.
To minimize distortion, the output stage is formed by the Darlington pair of Q2 and Q4, Q7 and Q11, while Q8 and Q9 provide constant current through the bias chain. In Darlington pair, two bipolar transistors consist this compound structure wherein the current amplified by the first transistor is amplified by the second transistor. This configuration gives a much higher current gain than each transistor taken separately and, in the case of integrated devices, can take less space than two individual transistors because they can use a shared collector. Integrated Darlington pairs come packaged in transistor-like integrated circuit packages.
Application
Amplifiers may be used in several industries such as: - Optical amplifiers - amplifying light through the process of stimulated emission
- Mechanical amplifiers – used in the pre-electronic era in specialized applications
- Johnsen-Rahbek effect amplifier – the earliest form of audio power amplifier
- Rotating electrical machinery amplifier - provides amplification of electrical signals by the conversion of mechanical energy to electrical energy
- Magnetic amplifier - a transformer-like device that makes use of the saturation of magnetic materials to produce amplification
- Carbon microphone - one of the first devices used to amplify signals
- Musical instrument audio amplifier - used to amplify signals such as music or speech
- Klystrons – a type of microwave amplifier that is ill-suited for light-weight mobile applications
- Travelling wave tube (TWT) amplifier – a type for microwave amplifier used for high power amplification at low microwave frequencies
- Distributed amplifiers - split the signal and amplify each portion separately in order to achieve higher bandwidth than can be obtained from a single amplifying device using transmission lines
- Oscilloscope vertical amplifiers - used to deal with video signals to drive an oscilloscope display tube and can have bandwidths of about 500 MHz
- Video amplifiers - deal with video signals and have varying bandwidths depending on whether the video signal is for SDTV, EDTV, HDTV 720p or 1080i/p
- Fully differential amplifiers (FDA) - a solid state integrated circuit amplifier which employs external feedback for control of its transfer function or gain
- Operational amplifiers (op-amps) - an amplifier circuit with very high open loop gain and differential inputs which employs external feedback for control of its transfer function or gain
- Transistor amplifiers - magnifies an input signal to yield a significantly larger output signal
- Vacuum tube or valve amplifiers - cost effective in high power applications such as radar, countermeasures equipment, or communications equipment
- Power amplifier - a relative term with respect to the amount of power delivered to the load and/or sourced by the supply circuit
Source:www.zen22142.zen.co.uk/Circuits/Audio/amp15.htm
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