Lecture 16

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

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

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

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

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern