can't find good complementary transistors

[keantoken]

I have had a problem with supposedly complementary transistors. It seems that many transistors that are "complementary" aren't really all that good twins. I need strongly complementary transistor pairs! I have seen a lot of 2N3904/2N3906 pairs but high-end circuits don't use such low-power transistors! Could someone list some good complementary pairs? I can't hope to achieve good amps if I don't know of any truly complementary transistors! Any help appreciated!

[singa]

Your post is not clear or specific enough.You don't expect 2n3904/2n3906 to be high power they are small signal transistors.The reason you don't see them in high end circuits is because they are not low noise types.There are no truely complementary pnp/npn transistors because of semiconductor properties/physics.What you get is close/similar characterics,this is not a perfect world.What do you really need,small signal or high power output transistors (presumably bipolar type)?Check the solid state forum.

[keantoken]

I am needing low-noise and high-power, maybe 2-4A at 60V for output pairs. I have read a book about semiconductor design and I know that transistors can't always be made perfectly complementary bacause of different doping elements needed for P and N matierials. I have heard that GaAs transistors are good, low noise but I don't know about current and voltage handling capabilities. Yes, I need bipolar. Sorry for the utterly bewildering lack of specifics, I can do that sometimes

[rtarbell]

I would suggest going to ON Semiconductor's website:

www.onsemi.com

and using their parametric search for bipolar transistors. You should be able to come up with something in your range of power, but I'm not too sure about noise (most low noise transistors are small signal and very low power).

[Leolabs]

Some Japanese names such as Toshiba does manufacture low noise BJTs with high voltage rating.

[singa]

originally by keantoken

I am needing low-noise and high-power, maybe 2-4A at 60V for output pairs.

For 1A and above it is assumed you would have taken care of noise .Now it's about voltage and current delivery. Motorola or now ON Semiconductor has an old favourite specifically designed for audio which is MJE15031/28 @8A, or BD240, TIP31/41. etc.

[keantoken]

I just tried the MJE15031/28 pair and they weren't similar enough. I have also tried the MJE15031/30 pair and they were better... I am building a symmetrical amplifier that uses more pnp's than npn's on one side and vice-versa. I think that the differences are being amplified... I guess my design needs strongly complementary transistors... From my amplifier design it might be obvious that I know barely anything about biasing transistors. I can bias a standard common-emitter, but I can't really understand how to bias Q3-Q6, but I think I am getting there. It probably isn't the best design but I don't think it's the worst either. At least it's a start, I think I might need another output pair if I were to design it to someone else's taste though. Although this circuit was posted for all to see and criticize, at lest help me to get it working! Here it is:

[Tim__x]

Stop just throwing transistors together. Read those links I gave you a few threads ago. Learn how standard topologies work before creating your own. Try to analize a two stage LTP-VAS amplifier first, just three transistors, three resistors and one capacitor.

[Tim__x]

Here's a (stripped down to the bare essentials) example.

P.S. R4 is the load i.e. the input of the next amplifier. Note how it goes from the output of the amplifier to ground.

[sawreyrw]

Tim_x,

You must be the guy who posted those links. That was a nice gesture; I think keantoken looked at them, but obviously, he didn't spend much time trying to understand them. keantoken may be smart enough to figure out how to bias transistors, but he clearly hasn't demonstrated it yet. keantoken, I would like to see you show a properly biased common emitter stage. Make it simple, one transistor with a current gain of 100, 3 resistors Rb, Rc, and Re with a couple of supplies; Vcc and Vbb. If he can't do this, he's lost.

Rick