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Old 3rd March 2003, 10:27 AM   #1
Mambo is offline Mambo  Italy
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Default Aleph clones using BJT

Are there any drawbacks upon building an Aleph clone all with BJTs ?

Like
- KSA1220A/MJE350 in the input stage with MJE15033 as current source
- Darlingtons MJ11032/MJ11016 or "custom darlingotns" with MJE243+MJ15003 or MJL3281

I'm simulating such a configuration and it seems to work ok, at least for DC operating point and transient analysis.

Thank You
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Old 3rd March 2003, 04:25 PM   #2
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No reason why it couldn't work.
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Old 3rd March 2003, 04:42 PM   #3
DRC is offline DRC  United Kingdom
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Lightbulb And ....

Quote:
Mambo wrote
Are there any drawbacks upon building an Aleph clone all with BJTs ?
Quote:
Nelson Pass wrote
No reason why it couldn't work.
How about and AlephX in BJT flavour ?
Has anyone tried (built / simulated) this ?

Dave
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Old 3rd March 2003, 08:32 PM   #4
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Mosfets are favored because of their high input impedance
and also because their high Vgs makes it easy to insert control
circuits that operate at 4 volts or so, rather than the 1.4 volts
seen in a darlington.
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Old 4th March 2003, 09:07 AM   #5
Mambo is offline Mambo  Italy
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The lower input ipedance of BJT requires higher current from the input differential pair; I'm getting good results (in simulation) with about 25 mA each.

Due to their lower Collector-Emiter on resistence BJTs should give you a lower output impedence also for low power versions of the clones (A5 and A3) and thus a better control like the big Aleph 1.2 and 2.
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