How to choose VAS current

[JeffYoung]

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?

 

[Zen Mod]

pretty much same thing , if well filtered

 

[JeffYoung]

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.

 

[Itsmee]

...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.