[enemigo]

What are the requirements for a transistor to be used for calss A biasing (cascode), like in a Pimeta?

I have not measured or read the datasheet yet, but I was told the 2N5457 will handle 10mA, so that sould be ok at least.

Knut

 

[Dreamslacker]

Quote:

Originally Posted by enemigo What are the requirements for a transistor to be used for calss A biasing (cascode), like in a Pimeta? I have not measured or read the datasheet yet, but I was told the 2N5457 will handle 10mA, so that sould be ok at least. Knut

The 2N5457 has a maximum IDss of 5.0mA and typically, it's actually nearer to 1.X mA. It's sufficient for an opamp driving buffers but not sufficient for use as rail isolation Jfet's in the PPA.
You'd want to measure the IDss of the individual Jfets if you're using the 2N5457 for both Q1 and Q2.

 

[enemigo]

Thanks! I'll measure them and see if they'll do for biasing. I will be using them for both Q1 and Q2.

Found out I had another question, I'll try posting them here before making a new thread.

Can I increase the current capacity of the PSU by putting two TLE2426's in parallell?

Knut

 

[steinchen]

no, the tle2426 is a rail splitter providing a virtual ground, it's not a regulator

 

[enemigo]

Quote:

Originally Posted by steinchen no, the tle2426 is a rail splitter providing a virtual ground, it's not a regulator

I know it's a rail splitter, and not a regulator, but I didn't know that was required to have any effect from wiring it in parallell

Knut

 

[tangent]

Quote:

Can I increase the current capacity of the PSU by putting two TLE2426's in parallell?

The evidence is that this can be done (see PPA) under some conditions. But in the PPA, the currents involved are very small, since most of the "ground" current is handled by the ground channel. Also, it's arguable that the TLE2426es aren't truly in parallel in the PPA since their inputs aren't directly connnected.

In an amp more like the MINT, where the TLE2426 is the sole source/sink of ground currents, I don't think paralleling is a good idea. A TLE2426 is, after all, a voltage source, and the rule is to never directly parallel voltage sources.

Have you studied my virtual ground article?

 

[enemigo]

I've read your virtual ground article many times, it's great!

I guess I'll just build my Pimeta with a TLE, if no one recomends using buffer based vgnd with a BUF634 (DIP8).

BTW, tangent, I'd appreciate any comments to my post "the figures and values behind a cmoy!?" - http://www6.head-fi.org/forums/showthread.php?t=105289

Thanks
Knut