loading effect

Thread Starter


Joined Jul 13, 2004
Why should be the input impedance of an amplifier be high and the output impedance be low?
What happens due to these impedances when they are used in multistage amplifiers.
What is loading effect.
Explain me in detail.
Thanx for the help.


Joined Jan 22, 2004

i will try to explain as simply as i can but the topic you have asked deserves to be a book. likewise the answer is in electronic books.

when the signal source Z is higher than the input Z of an amplifier, the result will be burn out of the signal source. meaning the input amp. will be drawing more current from the source than it can provide. if there is no burn out, oscillation will occur.

that principle of Z is applicable to every stage of amplification. the load should always be higher than the driver.

let's take the case of an audio power amp. suppose it's rated at 3A output @ 8ohms lspkr. load. now if you are going to connect a load or 2ohms. how much current will it draw? it will draw as much as 12A. so in effect the output stage of the amp will be driven very hard to comply with that drawn current of 12A. the result - burn out. :rolleyes: