hv transistors for ltp ??

Hi gurus, recommend me some high voltage transistors for a long tailed pair with supply voltage: +-30-50-60V ;) :)

I learned how to design discrete op amp and need test :D
I tested with 549 and 559.

If I decide to use not so simple LTP I would like to add only two more transistors and here is another quest. Up or Down ?
Current mirror or current source/sink ?
Only one! Which is better ? Any recommendations ?

And how to fight this 0.007% THD :D
 

Attachments

  • LTP_FINALLY.PNG
    LTP_FINALLY.PNG
    74 KB · Views: 234
BC546/556 will cover all your voltages.

On the other hand, you can cascode the collectors with some high voltage transistors like 2N5551/5401.

Then, to lower the distortion in this kind of topology, you can:
- add a current mirror (dynamic load for LTP);
- add an emitter follower between LTP and VAS.

current mirror will give you more advantage, then the current source.
 
Tnk u all :)
My amp sounds fantastic with an op-amp, lets see now with a pair.

P.S. Paralleling 5532 and 072 is very successful, big synergi. bass from 5532 and highs from 072. i soldered "ic on ic", "ic on top of the other".

P.S.2 vzaichenko, what means to cascode a collector ? Firstly i understood to add a current mirror.
 
Last edited:
Hey, with current mirror outputs nothing :confused:

Aand for newbies -> How to design Discrete Operational Amplifier - Design Guide - Theory - Bart HRK

P.S. oops screenshot error but its the same with the fb connection

You need to add degeneration resistor between the Q3 emitter and the rail, otherwise you don't let your mirror working - it's only 0.7V between the rail and the base of Q3 now.
and use PNP with emitter degen.
Better if you add EF helper to feed the VAS. See D.Self and many others.
 
An example.

As you can see, with a cascode, your LTP collectors only see the voltage you set with a zener (or some other way) minus 0.7V (cascode's Vbe).

Also note the emitter follower.

just not work :mad:@

P.S. look @ this is more powerful

[IMGHTTPDEAD]http://sound.westhost.com/ism-fig12b.gif[/IMGHTTPDEAD]
[IMGHTTPDEAD]http://sound.westhost.com/ism-fig12a.gif[/IMGHTTPDEAD]
 

Attachments

  • wtf.PNG
    wtf.PNG
    76.6 KB · Views: 103
Last edited: