tag:blogger.com,1999:blog-7057630065429233264.post6495578910174961300..comments2024-03-28T10:51:44.181+01:00Comments on Paul's DIY electronics blog: Building a Differential Amplifier Probepaulvhttp://www.blogger.com/profile/11421488581167758443noreply@blogger.comBlogger54125tag:blogger.com,1999:blog-7057630065429233264.post-34112838265729900972024-02-10T22:10:18.439+01:002024-02-10T22:10:18.439+01:00Hi Paul,
I've solved the problem. Both trimm...Hi Paul,<br /><br /><br />I've solved the problem. Both trimmers (C5 and C10) weren't making contact with the ground. After fixing that, everything proceeded okay.I notice a bit more noise (at 20mV/div) compared to how it looks on your oscillograms. I limited the bandwidth to 20MHz when i measured the noise.<br />https://postimg.cc/gallery/zXz70R9 <br />Otherwise, it seems quite accurate.<br />Many thanks for your contribution to this project.Mihai85noreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-69532562308870707212024-02-09T11:11:54.925+01:002024-02-09T11:11:54.925+01:00My assumption is that you have a bad solder joint ...My assumption is that you have a bad solder joint or a bad part. The adjustment should work really well.paulvhttps://www.blogger.com/profile/11421488581167758443noreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-22537671052471908732024-02-09T11:01:36.636+01:002024-02-09T11:01:36.636+01:00I did some more tests. I replaced c7 and c12 of 22...<br />I did some more tests. I replaced c7 and c12 of 22pf with 27pf and it still could not be compensated. The spike remained. Then I put the 22pf capacitors in parallel with the 27pf capacitors. The voltage peak has been reduced, but it still does not respond to the adjustment of c5 and c10. Can the trimmers be defective? I soldered them by heating the pcb from the back with Sn/Pb paste with a melting point of 183 celsius.<br />I put some captures with (22pF||27pf) : https://postimg.cc/gallery/mMzt9hv. I used the 1kHz scope callibration output , 2n7000 transistor and the adjustable power supply.<br />(Please delete the previous comment if it's possible.)<br /><br />Regards,Mihai85noreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-80566883065066855532024-02-09T10:51:54.734+01:002024-02-09T10:51:54.734+01:00I did some more tests. I replaced c7 and c12 of 22...I did some more tests. I replaced c7 and c12 of 22pf with 27pf and it still could not be compensated. The spike remained. Then I put the 22pf capacitors in parallel with the 27pf capacitors(22pF||27pf). The voltage peak has been reduced, but it still does not respond to the adjustment of c5 and c10. Can the trimmers be defective? I soldered them by heating the pcb from the back with Sn/Pb paste with a melting point of 183 celsius. <br />I put some captures cu 27pf||22pf:https://postimg.cc/gallery/mMzt9hv<br />Am folosit iesirea de 1kHz a osciloscopului ,tranzistor 2n7000 si sursa reglabila. <br />Regars!Mihai85noreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-73948985751026391402024-02-07T11:40:44.785+01:002024-02-07T11:40:44.785+01:00Sorry, I didn't specify at the beginning, it&#...Sorry, I didn't specify at the beginning, it's the standard version(for the moment) https://cdn.hackaday.io/images/5310021589137099149.jpg. At the moment I haven't changed anything.I respected all the values in the scheme/boom.<br />Thank you for your support.Mihai 85noreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-12632789112060076932024-02-07T10:49:08.883+01:002024-02-07T10:49:08.883+01:00Well done Mihai85, can you share the attenuation f...Well done Mihai85, can you share the attenuation factor and the component changes you made?<br />I've added your picture of the probe.paulvhttps://www.blogger.com/profile/11421488581167758443noreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-4916956327961574262024-02-07T09:33:50.809+01:002024-02-07T09:33:50.809+01:00https://postimg.cc/gallery/jqRqbsjhttps://postimg.cc/gallery/jqRqbsjMihai85noreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-88180406363702710292024-02-07T09:25:12.831+01:002024-02-07T09:25:12.831+01:00Hi Paul,
I also assembled the probe.
I proceeded ...Hi Paul,<br /><br />I also assembled the probe.<br />I proceeded to calibrate it.<br />It worked the first time, I adjusted R11 succesfully but it does not respond to the adjustment of c5 and c10. I guess I have to gradually decrease their value (simultaneously?) to 20,18,10pF.<br />Thank you!Mihai85noreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-89433154793087475902024-01-22T12:26:00.333+01:002024-01-22T12:26:00.333+01:00Hi Mihai85,
I'm not aware of anybody that chan...Hi Mihai85,<br />I'm not aware of anybody that changes the attenuation.<br />It can be done, but realize that this can be more involved than you anticipate.<br />Have a good look at my Blog for details, and also visit the Blog that Bud put together.<br /><br />If you do embark on this, please let us know so others can benefit.<br /><br />Success,<br /><br />Paulpaulvhttps://www.blogger.com/profile/11421488581167758443noreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-67582736329233241462024-01-22T12:08:54.053+01:002024-01-22T12:08:54.053+01:00Hello!
I'm about to build the probe.
What wou...Hello!<br />I'm about to build the probe. <br />What would be the values/modifications for 100x or 250x attenuation. Has anyone tested?<br /><br />Regards,<br />MihaiMihai85noreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-91552068588493524542024-01-13T11:00:40.279+01:002024-01-13T11:00:40.279+01:00Anonymous,
Unfortunately, I have no idea where the...Anonymous,<br />Unfortunately, I have no idea where the excessive noise is coming from and nobody reported this issue with a solution.<br />There are two possible sources that come to mind. An issue with the power supply or the rails and of course, the Opamps. Can you isolate the output Opamp and measure the output of the other two with a shorted input to hunt down the issue?<br /><br />Sorry, I can't provide more help.<br />Paul<br />paulvhttps://www.blogger.com/profile/11421488581167758443noreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-82304916802181445512024-01-13T10:04:34.366+01:002024-01-13T10:04:34.366+01:00I have the same high noise issue that another user...I have the same high noise issue that another user has reported. I tried to switch back and forth different components without any improvement (I have not changed the LTC6269 and LTC6268). Someone has found where the problem comes from? I used two different oscilloscope (Siglent and Rohde); bought components from Digikey and pcb from jlcpcb. An issue with the LTC6269 quality?<br />thanksAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-71086263573143292422023-10-29T16:35:01.173+01:002023-10-29T16:35:01.173+01:00Why don't you look yourself? Mouser has 48.000...Why don't you look yourself? Mouser has 48.000 in stock at this moment.paulvhttps://www.blogger.com/profile/11421488581167758443noreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-78383963332150192122023-10-27T08:59:38.459+02:002023-10-27T08:59:38.459+02:00What about LM8261M5X/NOPB? 2.5V supplyWhat about LM8261M5X/NOPB? 2.5V supplyAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-24879670361225557752023-10-26T23:17:28.211+02:002023-10-26T23:17:28.211+02:00Mouser has 18,839 in stock.Mouser has 18,839 in stock.paulvhttps://www.blogger.com/profile/11421488581167758443noreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-68128940163738334212023-10-26T18:48:50.242+02:002023-10-26T18:48:50.242+02:00Hi!
Its hard to get LM7301IM5X/NOPB IC. Is there ...Hi! <br />Its hard to get LM7301IM5X/NOPB IC. Is there any alternative part?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-64277219614629752472023-10-23T17:37:01.956+02:002023-10-23T17:37:01.956+02:00No, there is no JLPCB project.No, there is no JLPCB project.paulvhttps://www.blogger.com/profile/11421488581167758443noreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-36898403847168232912023-10-20T20:06:16.549+02:002023-10-20T20:06:16.549+02:00Hi!
I found project on PCBWAY. https://www.pcbway....Hi!<br />I found project on PCBWAY. https://www.pcbway.com/project/shareproject/100MHz_Differential_Probe_bb22e131.html<br />Is there also project on JLCPCB?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-9200067154835692582022-11-03T14:58:03.680+01:002022-11-03T14:58:03.680+01:00I got an email about a question from (an) Anomymou...I got an email about a question from (an) Anomymous poster but I don't see the post here yet.<br />The question was if it is possible to use the LTC6268HS6 version and Bud replied that it can be used. The only difference is that the H version has a wider temperature range — -40C to 125C.paulvhttps://www.blogger.com/profile/11421488581167758443noreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-54398833804154393792022-11-02T11:21:59.554+01:002022-11-02T11:21:59.554+01:00Hi Paul,
How do you think, would it work with LTC...Hi Paul, <br />How do you think, would it work with LTC6268HS6?<br />The only difference I can see is higher Input Bias Current of 4pA vs 0.9pA in IS6.<br />Current lead times for those chips are ridiculous, and I was only able to find HS6 in stock.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-49516717305144720172021-11-14T15:02:02.746+01:002021-11-14T15:02:02.746+01:00Thanks a lot for sharing, great stuff!Thanks a lot for sharing, great stuff!Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-302258650354407772021-08-20T09:32:49.964+02:002021-08-20T09:32:49.964+02:00The split supply is indeed needed to power the Opa...The split supply is indeed needed to power the Opamps, and we used the most economic and best solution to create it. It does not influence the BW of the probe itself.paulvhttps://www.blogger.com/profile/11421488581167758443noreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-2154457261112609752021-08-19T22:00:45.605+02:002021-08-19T22:00:45.605+02:00I just want to ask about virtual ground created wi...I just want to ask about virtual ground created with split resistors and opamp unity buffer. Is it realy needed and wanted that unity buffer has full BW? I'd rather limit BW to improve virtual ground stability. Just idea.dr.eMhttps://www.blogger.com/profile/00175580267570497934noreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-23375566228665434342021-06-21T10:32:00.164+02:002021-06-21T10:32:00.164+02:00The noise you are seeing is not normal. However, i...The noise you are seeing is not normal. However, it's difficult to give you a number because every DSO is different. As an example, my RIGOL DS2072 is very noisy below 50mV/Div. The 20mV noise level at shorted inputs and an input factor x10 is what I measured on this DSO and there is a picture shown in the Blog.<br /><br />Could the noise come from other equipment or devices that finds it's way into the probe?paulvhttps://www.blogger.com/profile/11421488581167758443noreply@blogger.comtag:blogger.com,1999:blog-7057630065429233264.post-21702322157853151932021-06-20T13:59:04.265+02:002021-06-20T13:59:04.265+02:00Hi,
I made this probe, but I seem to be getting ab...Hi,<br />I made this probe, but I seem to be getting about up to 100mV of noise with inputs shorted. What is the noise measurement with x10 scaling factored in on the oscilloscope? I see ~10mV talked about with scope on x10, is this really true? I've tried debugging, removing and reattaching opamps, checking for shorts etc. Nothing gets me to around 10mV roughly. And other than that, the probe works and calibrated just fine. Thanks.Anonymousnoreply@blogger.com