transistor current sources basic Wilson Widlar all 3 are current mirrors too.

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United States 240mains
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Published on ● Video Link: https://www.youtube.com/watch?v=B8hs9hZ94xM


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2

sorry bout the repost,...again,...added 2 extra frames.
based on book:
Microelectronic circuits second edition
ISBN 0-03-007328-6
pages
513 , 551 , 158 , 745 , 401 , 460 , 516
EBJ area 402, 404, 509, 516, 460 ,
I just ran the Eqs. on the Widlar current source, in the same way as for the
Basic current source and the Wilson current source.
By starting at the emitters.
Since the Widlar is not an exact\balanced mirror
due to the emitter resistor, I start with IE for Q1 and IE / 100 for Q2,
because IREF is 1ma and Iout is 10 ua .
After writng the Eqs. and solving for the current gain Iout / IREF =

1
--------------------------------
100 + 100/B + 1/B

since 1/B is insignificant to 100 ,
and since 100/B is mostly insignificant to 100 ,
the Widlar current gain here is approx. 1 / 100 ( No B beta in the gain Eq. ).
beta has a minimal effect on stabilty of the Widlar current source.
Widlar nailed it way back in 1960 something,....
Plus, the Zout can be over 50 meg ohm for this BJT Widlar configuration.

note:
Basic current source is an exact\balanced current mirror
Wilson current source is an exact\balanced current mirror
Widlar current source is not balanced, because IREF does NOT = Iout ,
due the the presence of emitter resistor RE of Q2 .



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current mirrors