New amp results

[nikwal]

Damn ..so many transistors, is it really worth it?
... I'mr working on an amp http://hem.bredband.net/nikwal1/evo6.gif and i think mine's got toooo many transistors (not built/tested/values will change probably)

 

[CBS240]

Damn ..so many transistors, is it really worth it?
... I'mr working on an amp http://hem.bredband.net/nikwal1/evo6.gif and i think mine's got toooo many transistors (not built/tested/values will change probably)

Hi Nikwal

That was just the amp section There is also 2 reg circuits, complements, that have 18 each. Every transistor is SOT-23 and costs about 4 cents each, except the drivers, outputs, and Vbe multiplier. I believe the p-ch j-fets were 8 cents. The worst part about this circuit is matching these little buggers. I noticed a significant difference in performance between the Thompson mirror and just a simple one. I know of no other way to implement this. Sounds great though. There is just some minor stability issues to resolve yet, related to the input impeadance/filter and the output load. Too many stages can cause a phase difference problem, but my circuit just uses a basic topology where each section is upgraded. Really not complicated, just looks that way. Cascade j-fet CCS instead of single, higher gain in second diff, crossquad, bias feedback so both input and VAS stage is biased from same reference, ect.


Question about your circuit...How could the output ever reach more than 3V peak? It appears the bases of the output drivers set at +/- 6V minus Vgs is the voltage limit. You need your drivers to drive up to 28V + Vgs in order to get rail to rail operation from the source follower output arrangment. Perhaps my idea of using a larger regulated voltage for the amp section to drive the output stage could help you here.

I see then where you could add a lot more transistors cascodes, mirrors, ect...... I sugest you get the simple version funtioning first though.