cspirou Posted December 9, 2017 Report Share Posted December 9, 2017 Thanks @luvdunhill! I'm using the buffer with the ubal/bal board which have a 1.3kohm resistor to ground on the output so i don't think an additional resistor is necessary. Plus I already have the PCBs and the pins match. I am interested in buffers for another project though. Ill let you know. Quote Link to comment Share on other sites More sharing options...
Pars Posted December 10, 2017 Report Share Posted December 10, 2017 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. Those look pretty sweet Marc!Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
kevin gilmore Posted December 10, 2017 Report Share Posted December 10, 2017 what transistors are you using? Quote Link to comment Share on other sites More sharing options...
luvdunhill Posted December 10, 2017 Report Share Posted December 10, 2017 what transistors are you using?I am using 2SJ106/2SK208, BCM61/BCM62, PHPT610030-series.The 2SJ106 is the SMT version of the 2SJ103. The 2SK208 is the SMT version of 2SK246. Quote Link to comment Share on other sites More sharing options...
sbelyo Posted January 5, 2018 Author Report Share Posted January 5, 2018 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 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? Quote Link to comment Share on other sites More sharing options...
jose Posted January 5, 2018 Report Share Posted January 5, 2018 What OPA is recommended? Quote Link to comment Share on other sites More sharing options...
sbelyo Posted January 5, 2018 Author Report Share Posted January 5, 2018 good question, it may say on the silkscreen. I'll look at the board Nope, I was hoping. We'd have to ask kevin Quote Link to comment Share on other sites More sharing options...
cspirou Posted January 5, 2018 Report Share Posted January 5, 2018 Should be the same OP27 used in the Dynalo Quote Link to comment Share on other sites More sharing options...
jose Posted January 5, 2018 Report Share Posted January 5, 2018 In buffer and Un/bal board? Quote Link to comment Share on other sites More sharing options...
Pars Posted January 5, 2018 Report Share Posted January 5, 2018 The schematic I have says OP27. diffinput3.PDF.pdf 1 Quote Link to comment Share on other sites More sharing options...
jose Posted January 5, 2018 Report Share Posted January 5, 2018 Thanks Pars. On our boards we haven´t any reference. I guess that we can use the OP27 on the buffer too. Quote Link to comment Share on other sites More sharing options...
sbelyo Posted January 5, 2018 Author Report Share Posted January 5, 2018 So should we match P to P and N to N? Or that plus P to N? Quote Link to comment Share on other sites More sharing options...
jose Posted January 5, 2018 Report Share Posted January 5, 2018 If nothing says otherwise, I will try to match as closed as possible P to P and N to N. Quote Link to comment Share on other sites More sharing options...
sbelyo Posted January 5, 2018 Author Report Share Posted January 5, 2018 That's what I was thinking Quote Link to comment Share on other sites More sharing options...
sbelyo Posted January 23, 2018 Author Report Share Posted January 23, 2018 I ordered BC546B\556B I couldn't find the C for both. Anybody see a problem with the B? Quote Link to comment Share on other sites More sharing options...
cspirou Posted January 24, 2018 Report Share Posted January 24, 2018 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-2018-01https://www.rocelec.com/part/FAIFSCBC556CBU I haven't ordered from either place so I don't know what they are like. Quote Link to comment Share on other sites More sharing options...
sbelyo Posted January 24, 2018 Author Report Share Posted January 24, 2018 That first place had them both... Darn, guess I didn't search hard enough. I ordered 250 each of the B from arrow and a transistor tester off ebay. We'll see what kind of numbers I get. Quote Link to comment Share on other sites More sharing options...
sbelyo Posted January 30, 2018 Author Report Share Posted January 30, 2018 the transistor tester measures hFE and Vf. What's are acceptable values for this circuit? How closely should I match the devices? Quote Link to comment Share on other sites More sharing options...
Pars Posted January 30, 2018 Report Share Posted January 30, 2018 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.Sent from my iPhone using Tapatalk Quote Link to comment Share on other sites More sharing options...
sbelyo Posted January 30, 2018 Author Report Share Posted January 30, 2018 Got it... Is an hFE of 300 good enough for this circuit? Quote Link to comment Share on other sites More sharing options...
sbelyo Posted February 3, 2018 Author Report Share Posted February 3, 2018 The majority of what I'm seeing is 315 hFE after measuring 34 devices. Is 315 good enough? Quote Link to comment Share on other sites More sharing options...
Pars Posted February 3, 2018 Report Share Posted February 3, 2018 I would think so. That is in the upper half at least of the range for B devices. Quote Link to comment Share on other sites More sharing options...
sbelyo Posted February 3, 2018 Author Report Share Posted February 3, 2018 cool... I should be able to get them all tightly matched then. Quote Link to comment Share on other sites More sharing options...
jose Posted March 5, 2018 Report Share Posted March 5, 2018 Finally, can BTAs work? Quote Link to comment Share on other sites More sharing options...
Pars Posted March 5, 2018 Report Share Posted March 5, 2018 BTA is the newer B designation. Just wondering if MPSA06/56 could be used in place of these? Pinout is backwards (EBC vs. CBE for BCs). Quote Link to comment Share on other sites More sharing options...
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