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Matched transistors in Dynahi - Page 11

post #151 of 158
6/19/09 at 8:25pm
Copy of his email to me:


I can also make sure that the HFE of the PNP’s and NPN’s are close to each other, even though that’s not required.

I just checked, and since you are the first, I can supply:



4 x 2SA1358-Y @ HFE = 153

4 x 2SA1358-Y @ HFE = 154

4 x 2SA1358-Y @ HFE = 156

4 x 2SA1358-Y @ HFE = 158



4 x 2SC3421-Y @ HFE = 153

4 x 2SC3421-Y @ HFE = 153

4 x 2SC3421-Y @ HFE = 153

4 x 2SC3421-Y @ HFE = 154



Cream of the crop. Better matching than my first Dynamite. I’m jealous.

-Dan


And the following reply to mine was this:


Scott:

Glad to hear you got the parts. If you know anyone else who needs parts, let them know. I have bags and bags just sitting on the shelf “looking for love”.

-Dan

Gimme a PM for his shipped quote.
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post #152 of 158
6/19/09 at 8:30pm
Quote:
Originally Posted by Kruemelix View Post
<snip>

2SC3421
134
136
137
138
139
139
140
141
141
142
143
143
143
144
144
144
144
144
144
145
145
145
147
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148
150
151
151
151
153
154
154
154
154
154
155
155
156
156
156
158
159
160
161
161
162
166
169

2SA1358
195
196
197
197
199
199
199
200
200
201
202
203
203
203
203
203
204
204
204
205
205
205
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206
206
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207
208
210
211
211
211
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213
213
213
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215
216
223

<snip>
Quote:
Originally Posted by j4cbo View Post
Well, here's what I wound up with for the drive transistors:

Group 1
2SA1358Y: 148, 148, 150, 153; spread 5, average 149.75
2SC3421Y: 148, 148, 148, 149; spread 1, average 148.25

Group 2
2SA1358O: 128, 129, 129, 131: spread 3, average 129.25
2SC3421Y: 128, 130, 132, 133: spread 5, average 130.75

It's not perfect, but pretty good. Started with 20 of each.
Any other thoughts?

j4cbo went with a bit lower gain than what is in Kruemelix' mix. I have ~16-20 of each plus 4 "O" grade of each. I haven't measured the "O" grade SA1358s yet, but maybe they will overlap the 3421s. I may pick up another 20 of each in "Y" grade, or maybe just more 3421s to see if I get some that fall higher in the range. I also need to take a look at the SA1145 and SC2705s first in case I wind up needing some of those as well.
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post #153 of 158
6/19/09 at 8:49pm
I don't know what class of gain 1145/2705's your using, but I've been buying them at Mouser lately. You can get "O's" for $12.50 per 100 pcs. I've had few that were way off.
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post #154 of 158
6/19/09 at 8:54pm
I didn't even know that Mouser carried these- hehe. I still need to check mine as I probably have enough. I must have been composing your post and hadn't seen your previous one. Good idea; I should just buy some from Dan. If you get a chance, shoot that quote to me via PM.

Thanks!

Chris
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post #155 of 158
6/19/09 at 9:50pm
I dunno, unless they're matched on a heat sink at the proper base current, they won't be all that close I've found. I'd just buy two times as many as you need from Dan in consecutive Hfe units and regroup them yourself. The deal is, most people will just use a hfe meter, which is okay.. it will "work" but the only real way to know if you really have good matching in the output stage is a distortion analyzer after the fact. The temperature is such an important component here, as well as Ib...
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post #156 of 158
6/19/09 at 9:58pm
True dat.
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post #157 of 158
6/19/09 at 10:11pm
In matching these myself, I had set up a protoboard that the transistor will fit in with a fixed base resistor. I have one meter measuring Vrb, the other measuring Ic. I use a clothespin to clamp the DUT to a strip of aluminum (heatsink).

When I apply power, both Vrb and Ic go up pretty quickly. They do stabilize somewhat but never become really stable, at least as long as I have waited.

I was waiting for Vrb to hit a particular value (which it does within probably 15-20secs of applying power) and reading Ic at that voltage. From what you are saying regarding temp, it sounds like I would be better off waiting for it to stabilize and then grab the readings?

BTW, my readings are correlating with DigiPete's for the most part (not identical, but very similar).
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post #158 of 158
3/18/10 at 12:50pm
I just got back to doing this for the output devices since Scott (digger) sent me a few more to play with. I am using a piece of 1" x 1/8" aluminum as the heatsink, with a clothespin, and it seems to be working pretty consistently, and there is a plateau which the devices seem to reach with a couple of minutes.

I am using a plug-in breadboard with a 100K pot set to ~59K (same value as Digipete used) and noticed something strange. When I was measuring one of the devices I got from Digipete, the Ic was almost half of what it should have been at the test parameters (Vrb 29.35V, Rb of 59K). I also took another meter and measured the input voltage, and at this point it was LESS (26.xx Vdc) than the Vrb. Impossible. Removing the meter measuring Vrb, the input voltage went back to what it should have been, and Ic went from ~45mA back up to 80 something. Even the ammeters on my bench supply showed this fluctuation.

I guess this is due to meter loading effects? Either of my good DMMs do this (Protek 608 and HP 3468). The Protek will do uA, so, I put it in series to measure Ib, and this seems to be working (Ic is in the correct range).

Any comments, suggestions?
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