Good Transistors? (BJT)

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Morrist

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Joined 2002
#1
I'm planning to design and build a preamp and a power amp, both single ended, both using BJTs.

I know that my power amp will have a two stage configuration; first stage a voltage amp and second a current amp. I'm not sure whether the preamp will have one or two stages.

My question is: What transistors would suit such applications and are there significant differences in sonic characteristics from transistor to transistor? Naturally, I would like to try some of the better ones.

Any help would be greatly appreciated.

Morrist
 
#9
I use MJ21193/4 or MJL21193/4 output devices in almost all of my amplifiers. They handle enormous amounts of current and are highly reliable, as I have never had one go bad yet -- they have even survived a couple short circuit situations (oops!). If you are concerned about the best linearity (i.e. lowest distortion) I would check out the 2SC3281/2SA1302 pairs. Doug Self published a paper showing their exceptional distortion performance with varying impedances, compared to many other popular choices -- they are the basis of his "load invariant" low distortion amplifier design!

Happy amp building!
 
#10
Good BJT transistors...

Good BJT transistors.......

I second Randy's suggestion. The 2SC3281/2SA1302 are the most linear devices I know, and beat the ubiquitous mosfet hands down; they have nominally flat beta from 100mA to 7A! They are 12A 150W devices with ft of 30MHz and minimum beta of 60. Typically I measure around 100, so they are very easy to drive. Vceo max is listed as 200V, and in practice with sensible rail voltages (less than 50V) it is very difficult to kill them by exceeding SOAR ratings. More Vcc requires protection, of course.

A couple of years ago Toshiba announced they would be superseded; the new numbers are 2SC5200/2SA1943 and the older versions are proving very hard to obtain now. The replacements are identical except for Vceo which is now 230V.

I use these in the AKSA; they are superlative devices and I cannot recommend them highly enough. They are not cheap, but they are the best.

Cheers,

Hugh

www.printedelectronics.com:D
 
#12
OnSemi no longer lists the MJ1302/MJ3281; I would have preferred to use them in my Leach amplifier where the heatsinks
are designed for TO-3 style cases.

I'm changing over to MJ21193/94, if I can get them. I've now
gotten 10 of the latter but haven't found a local source for the former that will sell in small quantities. They're probably not
being counterfeited either. I'd prefer to build all my future
projects with these parts when I have to use TO-3 cases.

OnSemi now also lists the MJ21195/96, which have a slightly
higher SOA; probably identical to the -93/94 but binned out
better in testing. Haven't found a source that's stocking them.
Also available in MJL and MJW packages, I think.

I don't keep up with offerings from Sanken and others, and
don't know a thing about MOSFETs; there may be other devices
out there with good or even exceptional specifications.
 
#15
Driver Choice with 3281/1302

Morrist:

You can use the MJE15030/MJE15031 from On Semi.

Or the 2SC4793/2SA1837 from Toshiba. Both work fine, with the OnSemi device withstanding 8A surge delivery. In practice, with a 10R base stopper on the output devices, using the 15030/31 means you never blow drivers, but the Toshibas are fairly hardy, too, and a little faster (100MHz/70MHz).

Cheers,

Hugh

www.printedelectronics.com
 
#16
I've used BD139/140, 2SB649/2SD669, and TIP31C/32C without any problems. The 2SB/2SD devices have very high VCE ratings making them suitable for high power use. I use the others for amps less than 100w, depending on my budget!



Morrist said:
I'm going to have to give the MJL3281/1302 a try.

AKSA and R. McAnally, what have you two used in the past to drive the combination, or their equivalent.

Morrist
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