Lecture 16 - EEL 4930 Audio Engineering Electronics for...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
EEL 4930 Audio Engineering Lecture 16 Page 1 of 3 Electronics for Audio Engineering Amplifiers The basic function of an amplifier is to increase the amplitude of a signal. In practice, a signal applied to the input of an amplifier controls the flow of energy from a dc power supply (voltage source) so that a larger-amplitude copy of the input signal is provided at the output. Ideally, the output waveshape is identical to that of the input signal. This requires the amplifier to be linear , and to have wideband, flat (frequency-independent) frequency response . If the output signal is measured as the input signal is swept, the resulting plot of the output vs. the input is called the transfer curve . Usually the input and output signals are represented as voltages. At any instant of time, a snapshot of the values of currents and voltages in a circuit is called the (instantaneous) operating point . The operating point when the input signal is zero is called the quiescent operating point or Q point . The input signal is added to a constant (DC) value so that the output can swing above and below its zero-signal value. This is called biasing , and the resulting Q point may be called the bias point . The slope of a tangent to the transfer curve at the Q point is the gain of the amplifier. The gain is the ratio of a change in the output to a small change in the input. If the inputs and outputs are represented as voltages, the gain may be expressed in decibels as A dB = 20log 10 ( A V ) , where A V is the magnitude of the voltage gain. It is easiest to understand amplifier linearity by considering the response to sinusoidal inputs. An amplifier is linear if, whenever its input is a sinusoid (a single frequency), the output is a sinusoidal with the same frequency. This requires that the transfer curve be well-approximated by a line over the range of the input signal, as shown in the illustration to the right. The output is a mirror image of the input. Harmonic Distortion If the input is swept over parts of the transfer curve that are nonlinear (not well-approximated by a line), the output signal will not be exactly sinusoidal; instead, its shape is distorted . The distorted waveform
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/08/2011 for the course EEL 4930 taught by Professor Staff during the Spring '08 term at University of Florida.

Page1 / 3

Lecture 16 - EEL 4930 Audio Engineering Electronics for...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online