Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
Output impedance is the resistance to an AC or DC signal.
A modern audio amplifier has negative feedback which reduces its output impedance to about 0.04 ohms or less so that it damps resonances of a speaker very well.
When a speaker resonates it becomes a generator. The very low output impedance of an amplifier shorts the generation which stops the resonance.
Try it. Tap the cone of a woofer speaker when it is not connected to anything. It will resonate with a boooom sound.
Then short its two wires and tap it again. It will make a short duration thud or pop sound without resonating.
With such a low output impedance then the output voltage is very well regulated and therefore it barely changes when the amplifier is loaded or is without a load.
Then the speaker does exactly what the amplifier is doing.
An Ideal Voltage Source has zero output impedance [approximated by a wall outlet or a car battery], and its dual, an Ideal Current Source [approximated by a flourescent lamp ballast], has infinite output impedance.
Amplifier inputs can be voltage controlled or current controlled and their outputs can simulate voltage or current sources.
E.g., a bipolar junction transistor is a current controlled current source.
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
