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-   -   Very High-Gain PNP Transistors... (http://www.diyaudio.com/forums/solid-state/146983-very-high-gain-pnp-transistors.html)

EchoWars 4th July 2009 10:55 PM

Very High-Gain PNP Transistors...
 
...for use in differential pairs. Let's say our criteria are as follows:

1. TO-92 case (or similar). No dual parts, such as a 2SA798.
2. Usable Vceo, 65V or better.
3. Minimum Ic of 50mA.
4. Reasonable bandwidth, 100MHz min.
5. Being in current production would be nice, but otherwise reasonably easy to find.

The best I have found:
Fairchild KSA992. Consistant gains of between 410 ~ 470 @ 1mA.

Zetex ZTX795A. High gains, typically between 510 ~ 575 @1mA, with the occasional device measuring a bit over 600.

Fairchild BC556C. High gains, usually better than 500, but all over the map, from 500 to 650 or so. I always find it a pain to match a pair of devices with these.

A while back, I pulled a few TO-92 PNP transistors from an old 70's Japanese amp, and out of curiosity measured gain. Of the eight devices, the lowest one measured about 750 @ 1mA. All were fairly close to that. I meant to write down the number, but I can't now find the devices, or remember the number. I'm sure they were long out of production, but I wish I could remember what they were. Maybe the best devices were in the past...

Any devices I'm missing? Love to hear your thoughts.

KSTR 5th July 2009 12:50 AM

Hitachi 2SA1085E... those are getting scarce, unfortunately. And maybe a bit on the low side regarding ft and usable Ic, but low noise and low Cob.

- Klaus

EchoWars 5th July 2009 12:59 AM

Yes, those are very good, but tough to find.

B&D gives a cross to the Sanyo 2SA1016K, and if you can find the 'H' gain group, it promises gains from 480 to 960(!).

Terry Demol 5th July 2009 01:50 AM

Re: Very High-Gain PNP Transistors...
 
Quote:

Originally posted by EchoWars
...for use in differential pairs. Let's say our criteria are as follows:

1. TO-92 case (or similar). No dual parts, such as a 2SA798.
2. Usable Vceo, 65V or better.
3. Minimum Ic of 50mA.
4. Reasonable bandwidth, 100MHz min.
5. Being in current production would be nice, but otherwise reasonably easy to find.

The best I have found:
Fairchild KSA992. Consistant gains of between 410 ~ 470 @ 1mA.

Zetex ZTX795A. High gains, typically between 510 ~ 575 @1mA, with the occasional device measuring a bit over 600.

Fairchild BC556C. High gains, usually better than 500, but all over the map, from 500 to 650 or so. I always find it a pain to match a pair of devices with these.

A while back, I pulled a few TO-92 PNP transistors from an old 70's Japanese amp, and out of curiosity measured gain. Of the eight devices, the lowest one measured about 750 @ 1mA. All were fairly close to that. I meant to write down the number, but I can't now find the devices, or remember the number. I'm sure they were long out of production, but I wish I could remember what they were. Maybe the best devices were in the past...

Any devices I'm missing? Love to hear your thoughts.

2SA970 BL are pretty good and readily available.
120V / gain 350~700 / 100mA / 100MHz. All the ones I had on hand
measured gain >400.


cheers

Terry

EchoWars 5th July 2009 07:19 AM

Thanks Terry!

I had forgotten about the Toshiba 2SA970. I have a couple dozen of them, and a quick check shows gains between 515 and 530. Not bad.

But...I'd love to find something with consistant gains of >600.

Terry Demol 5th July 2009 11:17 AM

Quote:

Originally posted by EchoWars
Thanks Terry!

I had forgotten about the Toshiba 2SA970. I have a couple dozen of them, and a quick check shows gains between 515 and 530. Not bad.

But...I'd love to find something with consistant gains of >600.

No worries.

If I may ask, why do you need such high beta?

cheers

Terry

AndrewT 5th July 2009 12:05 PM

a872
a970
a992
a1015
a1016
a1083/4/5
b715/6

and a couple NPN that I can't find complements for
c1845
c3068, only 25Vce0
and finally
d755/6

StevenOH 5th July 2009 02:07 PM

Andrew,
2SA992-2SC1845
2SC3068 was developed without a compliment.

AndrewT 5th July 2009 02:22 PM

neither of my NEC datasheets for the a992 & c1845 refer to the other as the complement.

mlloyd1 5th July 2009 05:56 PM

is the 2SA872A series still available? i haven't bought any in a while. they might be useful here.

mlloyd1


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