Really? I have only used them in logarithmic amps and VCAs, long ago, for instrumentation, where the sole attraction was supermatching, to get an order of improvement on Motorola's then log. IC amps.
Just reviewing early Natsemi app. notes AN262 onward, I'm reminded that you don't see early audio apps for the LM394 so you may appreciate my different viewpoint, low noise instrumentation requirements notwithstanding.
Audio use is another matter, I guess, as they did get thrown into the front end of preamps and amps everywhere - only to be dropped a couple of models later, hardly seen since.
The NF is certainly low at 1nV/root Hz but no better than single transistor pairs in MAT02, SSM2210 etc. I have tended to think the low noise is a consequence of multiple transistors rather than my principal requirement of gain matching and low drift. When I eventually began to experiment with them in audio, the priority was LTP DC balance and NF was not particularly important, as we find in most commercial amplifiers.
Hello,
I made measurements on some of my transistors.
I used a PeakMeter PM8233D DVM to measure Vbe, whilst measuring
Hfe with a Duoyi DY294 transistor tester, @ Ib = 10µA.
The 2SA640 were LTP extracted from an old power amplifier.
I don't remenber the brand.
The BC557B and BC560C were baught from an eBay chinese seller.
They were presented as matched transistors.
So ??
I made measurements on some of my transistors.
I used a PeakMeter PM8233D DVM to measure Vbe, whilst measuring
Hfe with a Duoyi DY294 transistor tester, @ Ib = 10µA.
The 2SA640 were LTP extracted from an old power amplifier.
I don't remenber the brand.
The BC557B and BC560C were baught from an eBay chinese seller.
They were presented as matched transistors.
So ??
Attachments
what are the digits that look like an inverted "V"?
How did you measure VBR ce0?
Hello,
"what are the digits that look like an inverted "V"?" It's Volt.
"How did you measure VBR ce0?"
With the transistor tester Duoyi DY294.
- Review of the DY294 Digital Transistor Tester-Part 1 | Electronics Repair And Technology News
"what are the digits that look like an inverted "V"?" It's Volt.
"How did you measure VBR ce0?"
With the transistor tester Duoyi DY294.
- Review of the DY294 Digital Transistor Tester-Part 1 | Electronics Repair And Technology News
Attachments
Last edited:
!I haven't bought any in a while, but it seems like very professional here.
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YIY — Inverter / Voltage Stabilizer Professional Manufacturer!
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YIY — Inverter / Voltage Stabilizer Professional Manufacturer!
The way you wrote "1" is like inverted "V". I had no problem reading it even tho I didn't know about any European style.
I don't know why you made the test, as BC550c/560c is pretty standard low noise high gain (typically above 500) transistors, and OP seemed to want something better than that.
BUT, important information from your test is that they actually have such a high break down point!! (74v?). I have also believed that the rated max SOA characteristics in the datasheets are underrated for original products from top manufacturers. That's why I use Vceo=45V device all over the places.
If you can't find the real deal, they're basically two ECB pinout transistors side by side - you could epoxy together two KSA992 or similar to obtain the desired pinout (or maybe solder in first, then epoxy). Much like what people are doing to replace 2SA798s, except easier. Should the whole thing get too thick, you could probably sand off some of the rounded back.
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