Lazzer,
Every builder blows up a few transistor until they realise the pinout even if they do not understand the datasheet 'convention'. They are not expensive......
There is no point getting irritated with it; it is what it is. Anger prevents learning. The markings are always on top, metal 'tabs' are underneath, leads are pointing downwards, and the pinouts are always left to right. I have wandered the silicon crematorium so often I can recognise the tombstones.....
HD
Every builder blows up a few transistor until they realise the pinout even if they do not understand the datasheet 'convention'. They are not expensive......
There is no point getting irritated with it; it is what it is. Anger prevents learning. The markings are always on top, metal 'tabs' are underneath, leads are pointing downwards, and the pinouts are always left to right. I have wandered the silicon crematorium so often I can recognise the tombstones.....
HD
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Hi lazzer408,
This may help. I put it together for this reason while building the BAKSA. Columns are sortable. Click on the transistor name for the datasheet.
Driver Transistors
regards
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Hi lazzer408,
Not really possible. Any PCB designer will have their own library of "tried and true" components, especially the common ones like BD139, that have been used successfully on many previous PCBs.
No one would make an initial batch of 500 PCBs without going through at least one "test" batch.
regards
Member
Joined 2009
Paid Member
did you look on eBay recently.....at least it feels that way with some of the stuff you see 🙄
I should have said, no one that is posting in this thread would release a PCB to the community without a "test" batch. 😀
Wow, Greg, that's really great! Thanks a lot! Perhaps you might want to add the good old TO3 MJ21193/21194 pair to your list of output devices? At first glance the same as MJ15024/15025, but please have a look at their SOAR ratings and compare! Might be the result of their Perforated Emitter technology. Best regards!http://www.mouser.com/ds/2/308/MJ21193-D-108487.pdf
Greg - very cool reference. Added the link to our "Links" page 😉
Virtual Zero Audio - Useful Links
Cheers,
Valery
I'm not angry about it. My comment was more for entertainment purpose then explanation. As far as I knew, terminals were labeled from left to right.
Imagine an IC having the pins numbered backwards but the pin definitions are correct in the datasheet.
So I've read more then I wanted too about this topology. Carlos (or Aksa?) has it dialed down to a minimum design. I've yet to come to any conclusion as whether or not a CCS, current mirror, or VAS protector had a negative impact on the "sonic magic" of the bootstrapped amplifier.
Has anyone built just the bootstrap/driver/output stage and driven it with some other source? Perhapse an opamp? How much of a dxamp's magic is the LTP/VAS and how much of it is the bootstrap?
Has anyone built just the bootstrap/driver/output stage and driven it with some other source? Perhapse an opamp? How much of a dxamp's magic is the LTP/VAS and how much of it is the bootstrap?
Another question.
Is the BD140G safe with +/-45v rails? I feel I'm close to the limits of that device.
Is the BD140G safe with +/-45v rails? I feel I'm close to the limits of that device.
No, not safe at all. Both VAS and driver transistors may see up to rail-to-rail voltage (90V in your case), which is higher than the limit for BD140 (80V).
MJE340/350 pair is good in this case.
2SC3503/A1381 pair is even better, but in the circuit, initially designed for BD139/140 it's just a bit of an overkill.
MJE340/350 pair is good in this case.
2SC3503/A1381 pair is even better, but in the circuit, initially designed for BD139/140 it's just a bit of an overkill.
C3503/A1381 are 4.3X faster than MJE340/350 (using fT as a proxy for speed), and their datasheets value of Cob is a factor of 3.2 lower.
They are rated for 300V, 100mA and are housed in TO-126 packages.
They are rated for 300V, 100mA and are housed in TO-126 packages.
I've looked into both transistors mentioned. The 2SA1381 and the MJE350. Any preference to one over the other? I have the spice model for the MJE350, but not the 2SA1381.
The drivers I used (MJE15034 and MJE15035) are rated to 350v so no issues there.
The drivers I used (MJE15034 and MJE15035) are rated to 350v so no issues there.
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2SA1507 suitable?
160v
1.5a
1.5w
Ft 120mhz
hfe 100(min)
http://www.onsemi.com/pub_link/Collateral/EN2101-D.PDF
160v
1.5a
1.5w
Ft 120mhz
hfe 100(min)
http://www.onsemi.com/pub_link/Collateral/EN2101-D.PDF
As I mentioned, 2SC3503/A1381 are better transistors in general (initially designed for video applications), than MJE340/350.
Low Cob, high fT, high enough hFE. I use them extensively in my designs.
Here are the models that work well for me:
.MODEL 2SC3503C npn
+IS=40e-15 BF=170 VAF=769
+IKF=0.08 ISE=200e-15 NE=1.5 NF=1.0
+RB=75 RC=1.5 RE=0.1
+CJE=95e-12 MJE=0.35 VJE=0.75
+CJC=7e-12 MJC=0.35 VJC=0.75 FC=0.5
+TF=585e-12 XTF=10000 VTF=35 ITF=20
+TR=10e-9 BR=0.6 IKR=0.05
+EG=0.75 XTB=1.5 XTI=3 NC=1.5
+ISC=7e-15 NR=1.0 VAR=100 IRB=3e-6
+RBM=0.035 XCJC=1.0
.MODEL 2SA1381C pnp
+IS=50e-15 BF=160 VAF=328
+IKF=0.5 ISE=10e-15 NE=1.5 NF=1
+RB=17 RC=4.1 RE=0.05
+CJE=71e-12 MJE=0.35 VJE=0.75
+CJC=8e-12 MJC=0.35 VJC=0.55 FC=0.5
+TF=900e-12 XTF=10000 VTF=35 ITF=20
+TR=1e-9 BR=1.6 IKR=0.09
+EG=0.6 XTB=0.9 XTI=3 NC=2
+ISC=3.2e-10 VAR=100
Ok. It seems close to the BD140G but higher voltage. What's the Ft of a BD140G?
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