Amplifiers
description
Transcript of Amplifiers
Amplifiersa powerful beast
amplification
• amplification is the use of a small volatge/current to control a larger voltage/current. A change in the input is reflected a a proportional change in the output.
• the changing voltage/current is called the signal
• the amount of increase in output signal over input signal is called gain
line amplifiers• devices designed to increase signal
voltage
• most line amplifiers operate on standard signal level
• line amps isolate inputs and outputs and restore gain after signal processing
• amps that isolate sensitive portions are buffers and those that restore signal are boosters
unity-gain amplifiers
• purpose of the unity-gain amp is to relay signal without either increasing or decreasing its signal level
• unity-gain amplifiers are used as buffers and as the basic signal handling element in automatic gain control devices
preamplifiers
• is used to raise an extremely low-power signal to line level
• most transducers(phono pickups, microphones, tape heads) generate extremely low signal power
• preamps for mics are usually in the mixing console
• phono and tape require preamps located near the device
preamplifiers
• preamps are usually built into console, tape recorders, and other large pieces of audio equipment and rarely include any control
• exception is the variable gain control microphone preamp in mixing consoles
power amplifier• sole purpose is to boost a low-
voltage input signal, line level(.75 -1.0 volt) to a high-voltage output signal( power level)capable of efficiently driving a loudspeaker
• typically take a line level signal, power level of 3.3 milliwatts, and boost it to an output level of about 1 or 2 watts to as much as 100 to 200 watts
power amplifier• the power amplifier is very nearly a pure
current source highly susceptible to short circuits
• most amps have automatic power protection circuitry(parallel connections in speakers lowers impedance)
• damping factor to check ballistic nature of speakers, because the inertial movement of the cone acts a generator to produce counter emf in the circuit between the speaker and the amp
power amplifier• damping factor, the higher the
damping factor the more effective spurious signals are suppressed
• clipping occurs when the amplifier cannot produce a voltage output greater than the power supply then the waveform is flattened at the top or bottom. Clipping is a form of distortion that is particularly obnoxious