[sdiy] [POSSIBLE SPAM] Another satisfied Takuya Katayama Tempco customer.

[Csaba Zvekan]

Ian ,

I am by now means an electronic guru . And can not answer your  
question. All I know is that I have matched some transistors (BC547)  
for a VCO project (Yves VCO Yusynths  http://yusynth.net/Modular/EN/VCO/index.html
and compared with the LM394 SuperMatched Pair) . And find no  
noticeable difference in temperature drift or anything.
The only difference is the price  compare for yourself LM394 is 22.35$  
and two BC547 is 0.20$ . Ok you would still need to purchase a bunch  
to compared them. But you get the idea.
All though I must say that the precision OP-AMP OP490  is rather  
expensive ( 15.70$ @ farnell.com )  :( but hey , we want precision,  
right ? And it's not like we need to buy hundred of them. The rest of  
the project is rather cheap .
Make sure you handle measuring in the morning and touch the  
transistors with tweezers. Also give it some minutes to settle . You  
'll get the hang of it.
The original design I got from here:

http://electronicdesign.com/Articles/Index.cfm?AD=1&AD=1&ArticleID=6251

Csaba



On Jul 18, 2008, at 4:24 PM, Ian Fritz wrote:

> At 05:29 AM 7/18/2008, Csaba Zvekan wrote:
>> We SDIY people always need matched transistor pairs :
>>
>> that's why I recommend this:
>>
>> http://www.csaba.ch/index.php?option=com_content&task=view&id=14&Itemid=30
>
> Is there some advantage of this over a simple bridge circuit?  How  
> precisely can you measure the matching?
>
> Ian