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Old 11th Sep 2019, 1:58 pm   #13
G8HQP Dave
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Join Date: Sep 2008
Location: Solihull, West Midlands, UK.
Posts: 4,872
Default Re: Cathode follower line out - best practice

It is a useful rule of thumb for audio, when designing a source which may be asked to drive any reasonable load.

Dropping the quiescent current in a cathode follower doesn't just raise the output impedance (by reducing gm), it also reduces the available current to drive the load which may raise distortion. However, a 10k load is not too bad. A volt of signal will require 0.1mA of signal current so the quiescent current just needs to be a few mA.
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