| Author: | tubeswell (registered user: 107 posts ) |
| Date: | Sun, Aug 19th, 2012 @ 18:24 ( . ) |
From Merlin's 1st book, the output impedance of a cascode is Ra||ra2+ra1(u2+1) where: ra2 = upper triode's plate resistance ra1 = lower triode's plate resistance u2 = the amplification factor of the upper triode For most triodes ra+ra(u+1)>Ra, therefore Zout~=Ra which is why I was subsequently thinking that the output impedance wouldn't be high enough |
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