See page 6 of EN#39. For NPN connect the emitter to ground. Connect a
1.5 Meg resistor between the base and +15V, connect a multimeter
measuring ma (milliamps) between the collector (- lead on the meter) and
+15V. 1ma = HFE of 100, 2.5 ma = HFE of 250, etc. Just select two
transistors with close HFE. For PNP use -15V and reverse the meter
leads. I found that the 2N3904 and 2N3906 had quite different HFE. So
I could not match the NPNs with the PNPs at all. Just the pairs of each
kind.
Richard
1.5 Meg resistor between the base and +15V, connect a multimeter
measuring ma (milliamps) between the collector (- lead on the meter) and
+15V. 1ma = HFE of 100, 2.5 ma = HFE of 250, etc. Just select two
transistors with close HFE. For PNP use -15V and reverse the meter
leads. I found that the 2N3904 and 2N3906 had quite different HFE. So
I could not match the NPNs with the PNPs at all. Just the pairs of each
kind.
Richard
On 4/15/10 7:02 PM, Logic Analog wrote:
> curious myself.
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> does anyone have a link to the Electronotes technique described by Mr. Brewster???
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> thanx, MoogFool.
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> To: cgs_synth@yahoogroups.com
> CC: 23isgood@...
> From: pugix@...
> Date: Thu, 15 Apr 2010 14:48:09 -0400
> Subject: Re: [cgs_synth] CGS75 VCS
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> I hand-matched the two 3904s and the two 3906s. It is simple to do, but
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> a little hard to describe. I found the technique in Electronotes. How
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> important this is, I don't know.
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> Richard Brewster
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> http://pugix.com
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> On 4/15/10 2:36 PM, Pete wrote:
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>> I was wondering if the VCS would benefit from matching the transistors?
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>> pete
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> _________________________________________________________________
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