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AMV8 8th March 2011 08:39 PM

MJL1302 and MJL3281 best driver transistors
Could someone recomend the best driver transistors to use with output transistors MJL1302 and MJL3281.
These will be used in Class A and Class AB complementary power amplifiers of 50 W to 100 w output power with between 2 and 6 output transistors in parallel.
The MJL1302 and MJL3281 are fast high beta transistors and I am not sure which current transistors would make the best driver transistors.
Should I think about using these as output transistors and also as driver transistors?

Stormrider 8th March 2011 09:14 PM

2sa1837/2sc4793 or 2sa1930/2sc5171 are a good choice for medium power amps if you can get them.

Fairchild has some good TO126 devices for lower power uses, such as:


For really high power uses the OnSemi MJE15034/35 devices work, but they are not in the same class as the 1302/3281's.

djk 9th March 2011 01:36 AM

Carver used the A1302/C3281 for both drivers and outputs in some of his better amplifiers.

Bonsai 9th March 2011 03:37 AM

The OnSemi MJE15034/35 are great devices - they are fast (c. 30MHz Ft which is fine for the drivers) and because of their dissiaption capability, if you use them in a double or triple EF 'T' you can run them heavily in class A.

What are you using for your VAS transistors? These are probabl ythe most critical devices in any linear amp.

h_a 9th March 2011 06:34 AM


Sweet parts - one can even use them as hot running VAS.


john_ellis 9th March 2011 06:39 PM


I would recommend the A1837/C4793 becuase they have a higher ft than the MJE's

But the MJE's cuold be good for driving MJ21194/5 's (having ~5..6 MHz fT output is not always bad ... ). I used the old A968/C2238 with those and got .003%THD /100W, and the A1837/C4793 seem to be updated versions.


AMV8 10th March 2011 10:08 PM

Thanks for your input guys - you are much more up to date on currently available parts than I am.
I had been looking at what was available and before your input I had thought of using the MJL1302 and MJL3281 for output and driver with the 2sa1930 and 2sc5171 for the VAS stage. Over the years experience has taught me that the the transistors are the least linear device in an amplifier so I was trying to get parts of as good a quality as the MJL1302/3281 parts if possible for all the positions.
I should probably have also asked for any advise on the VAS transistors also - any recomendations?

Stormrider 10th March 2011 11:16 PM

Your design choices will be somewhat based on what you can get from a reputable dealer. A lot of the Japanese parts, and some US parts, are being heavily counterfeited.

These are some parts I've seen used in VAS stages in reputable designs with no particular order of preference; you need to use what's right for your design. The Fairchild and OnSemi parts will probably be easier to get than the Toshiba or Hitachi parts.

2SA1381/2SC3503 (KSA1381/KSC3503)
KSA1220/KSC2690 and 1220A/2690A

Bonsai 11th March 2011 02:41 AM

The 340 and 350 are not suitable for VAS transistors. For this function you want devicves with a very low Cob, which these devices dont have. The KSC1381/3503 are good VAS devices.

ostripper 11th March 2011 03:34 AM

A little Cob sounds Goooood. :D Look at all of ampslab's kits , dr. Bora's sigma , and too many other designs to count ... all with MJE340/350's as VAS. These all work and sound exquisite , even with these old devices. :confused:


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