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How to choose VAS current
How to choose VAS current
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Old 5th December 2018, 09:04 PM   #21
JeffYoung is offline JeffYoung  Ireland
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How to choose VAS current
On the double-BJT CCSs employed for the LTP and the VAS, I've seen them with the second leg taken to ground, and with the second leg taken to -V (as in the above drawings).

Are there advantages to either, or are they equivalent?
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Old 5th December 2018, 09:08 PM   #22
Zen Mod is offline Zen Mod  Serbia
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How to choose VAS current
pretty much same thing , if well filtered
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Old 5th December 2018, 09:54 PM   #23
JeffYoung is offline JeffYoung  Ireland
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How to choose VAS current
Thanks, ZM.

I ran into an interesting limit for the VAS current. Increasing the current requires increasing the LTP resistor to maintain a 0 DC offset. However, at some point the voltage drop over the LTP resistor starts to eat into your swing and clip the amplifier.
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Old 5th December 2018, 10:21 PM   #24
Itsmee is online now Itsmee  England
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How to choose VAS current
Quote:
Originally Posted by JeffYoung View Post
...with the second leg taken to ground, and with the second leg taken to -V...
It's only a personal opinion, so worth nothing.
I avoid connecting things to ground, idealy there should be no DC current flow on the 0V rail; the only current flow should be the input signal current, the output AC current should be returned to the PSU where it came from.
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