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Balanced to unbalanced board


sbelyo

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cspirou: I would add an input resistor to ground as well. You can match Q1 to Q3 and Q5 to Q7, but I don’t think matching is all that useful here. If you want to try another small SMD buffer, let me know. I have just ordered some boards now that I have verified their performance versus sims.
 
I can include matched Toshiba JFETs and the other dual package BJTs are available at Mouser.
 
0cab7578d0cbcbcf4e6f6b8699ba265d.jpg
 

Those look pretty sweet Marc!


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  • 4 weeks later...
On 1/20/2017 at 9:59 AM, kevin gilmore said:

it had better look like this

the output impedance is about 1k, working on the diamond buffer output now

diffinput3.jpg

I'm going to order the transistors for this and the buffers. 

1. I know that I have to match for hfe and Vbe but do I match all the N together and the P together or do I match N to P?

2. The highest hfe is the BC546\556 C, this only comes with formed leads.  Will I need to straighten them out, and if so I'm guessing there's no issue with that?

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  • 3 weeks later...
2 hours ago, sbelyo said:

I ordered BC546B\556B  I couldn't find the C for both.  Anybody see a problem with the B?

C has the highest hFe. B might be okay if you measure a bunch and take the highest measuring ones. It seems to be in stock here:

https://www.tme.eu/en/details/bc556c-dio/pnp-tht-transistors/diotec-semiconductor/bc556c/?utm_source=octopart.com&utm_medium=cpc&utm_campaign=compare-2018-01
https://www.rocelec.com/part/FAIFSCBC556CBU

I haven't ordered from either place so I don't know what they are like.

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I’d match for hFE, but also try to get Vf (also known as Vbe) as close as possible as well. I’d shoot for 5% if possible. Matching the N and P is often nigh impossible depending on device type. You just have to do the best you can.


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