Jaycee,
I have the same concern about replacing MJE340/350 pair too. May be, Motorolar doesn't have any better. I'll probably have to try some Japanese BJTs. I guess you also had experience with some osc, is that right?
So far, these pairs work fine as following:
MJE340/350 for +/- 60V and up
BD149/150 for +/- 40V and lower
I have the same concern about replacing MJE340/350 pair too. May be, Motorolar doesn't have any better. I'll probably have to try some Japanese BJTs. I guess you also had experience with some osc, is that right?
So far, these pairs work fine as following:
MJE340/350 for +/- 60V and up
BD149/150 for +/- 40V and lower
Yep, my choice would be 2SA1209/2SC2911 from Sanyo. They have a decent fT of 150MHz, a low Cob of 3pf, and are rated for 160V Vceo.
jaycee said:
i don't see what c6 and c7 are doing. they have no miller effect as there is no gain between the base and Vcc. all it seems to do is lower some extra pole down.
If you didn't have C6 and C7 on the board, the output would be oscillated unless you had a perfect PCB layout.
Yes,
I have used MPSA42/92 for VAS and they have done their beautiful work. I'm glad that you ask.
About dissipating heat, you don't have to worry much about because the max current applied for those is not larger than 10mA, depending upon the working voltage for each device. For a stable design, you don't want to set it at max, but about 5 mA
I have used MPSA42/92 for VAS and they have done their beautiful work. I'm glad that you ask.
About dissipating heat, you don't have to worry much about because the max current applied for those is not larger than 10mA, depending upon the working voltage for each device. For a stable design, you don't want to set it at max, but about 5 mA
Hm... i tend to run the VAS at about 8-10mA, so I prefer a TO-126 device for this job. I also like to be able to heatsink them, and heatsinking a TO92 package is a pain.
Currently simulating with KSC3503/KSA1381 from Fairchild (as they have models) but the end result will probably use 2SC2911/2SA1209 from Sanyo. They are very similar in spec, speed and Cob so they should work fine. My design is very similar to yours, just for 100W@8 ohms only, with a cascode in the LTP's, and the VAS EF-degenerated
Currently simulating with KSC3503/KSA1381 from Fairchild (as they have models) but the end result will probably use 2SC2911/2SA1209 from Sanyo. They are very similar in spec, speed and Cob so they should work fine. My design is very similar to yours, just for 100W@8 ohms only, with a cascode in the LTP's, and the VAS EF-degenerated
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