# SMD Equivalent for BC547? **URL:** \ **Category:** DIY STUFF\ **Created:** [January 18, 2021, 10:35am UTC](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727 "2021-01-18T10:35:08Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![popflier](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/popflier/32/80_2.png) [@popflier](https://lookmumnocomputer.discourse.group/u/popflier)\ **Post date:** [January 18, 2021, 10:35am UTC](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727/1 "2021-01-18T10:35:08Z")
Can someone tell me what the SMD equivalent would be for a BC547 please? This is for @CTorp K25 Gate to Trigger module. I need to do an SMD version for my case but I am not sure what to substitute it with. I am not seeing that there are any SMD versions of the BC547. Here’s a link to the schematic. [https://github.com/CTorpin/k25utilities/blob/main/DG2T.pdf](https://github.com/CTorpin/k25utilities/blob/main/DG2T.pdf) ---
**Author:** ![eric](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@eric](https://lookmumnocomputer.discourse.group/u/eric)\ **Post date:** [January 18, 2021, 10:46am UTC](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727/2 "2021-01-18T10:46:38Z")
Any NPN transistor will do there. 2N3904 for example. (that should be MMBT3904 in SMD I think) Still, test on a breadboard with a good old human sized transistor first… ---
**Author:** ![popflier](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/popflier/32/80_2.png) [@popflier](https://lookmumnocomputer.discourse.group/u/popflier)\ **Post date:** [January 18, 2021, 10:50am UTC](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727/3 "2021-01-18T10:50:43Z")
Thanks. Breadboarding would take me a year to sort out, unfortunately. To be on the safe side could I have all of the other parts as SMD and leave the BC547 as through hole? I have the space on the PCB to do that. ---
**Author:** ![eric](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@eric](https://lookmumnocomputer.discourse.group/u/eric)\ **Post date:** [January 18, 2021, 12:44pm UTC](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727/4 "2021-01-18T12:44:37Z")
If you have the space, there is nothing against it. You can mix THT and SMD freely, they have the exact same electrical characteristics. Also, you could put both footprints (THT and SMD) on the PCB, and try with the MMBT3904. If it doesn’t work, unsolder it and put a BC547 in… And I think the '072 is overkill for driving the LEDs in this case. It is a trigger after all, that’s on or off, no subtle variations inbetween to show. The LED (with its current limiting resistor) could just be put in parallel with R10/R11 (or R12/R13 for the second channel). ---
**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\ **Post date:** [January 18, 2021, 1:35pm UTC](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727/5 "2021-01-18T13:35:30Z")
> The SMD versions of the BC547 are available as the BC847 (SOT-23), BC847W (SOT-323), BC850 (SOT-23) and BC850W (SOT-323). per [BC547 npn transistor datasheet pinout complementary pnp, replacement, pin configuration, substitute, equivalent smd](https://www.el-component.com/bipolar-transistors/bc547). There even are dual versions, e.g. BC847BPDW1, two transistors in one package. ---
**Author:** ![CTorp](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/ctorp/32/15023_2.png) [@CTorp](https://lookmumnocomputer.discourse.group/u/CTorp)\ **Post date:** [January 18, 2021, 1:49pm UTC](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727/6 "2021-01-18T13:49:02Z")
> [@eric](#): > > And I think the '072 is overkill Probably. I tried just doing the led and resistor off the output first and it pulled down the trigger output too much. Couple of transistors would be fine tho. Even with the 72 the pulse is so short the LED just barely lights up. ---
**Author:** ![eric](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@eric](https://lookmumnocomputer.discourse.group/u/eric)\ **Post date:** [January 18, 2021, 1:49pm UTC](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727/7 "2021-01-18T13:49:20Z")
Looks like BC847BPDW1 is a NPN/PNP combo… When I saw the pinout I told myself “cool you can mount it both way…”, then I noticed one is a NPN the other a PNP. ---
**Author:** ![eric](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@eric](https://lookmumnocomputer.discourse.group/u/eric)\ **Post date:** [January 18, 2021, 1:52pm UTC](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727/8 "2021-01-18T13:52:07Z")
Yeah, I didn’t try it : “I think” means I could be wrong 🙂 And soldering a 8 pin socket for the '072 is easier than 2 transistors, unless you got them with the pins in the correct shape for the footprint used. ---
**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\ **Post date:** [January 18, 2021, 2:53pm UTC](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727/9 "2021-01-18T14:53:35Z")
Right you are! The [BC847BDW1](https://www.mouser.com/datasheet/2/308/BC846BDW1T1_D-1802812.pdf) is dual NPN though. ---
**Author:** ![eric](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@eric](https://lookmumnocomputer.discourse.group/u/eric)\ **Post date:** [January 18, 2021, 2:57pm UTC](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727/10 "2021-01-18T14:57:53Z")
Man is this naming scheme obscure… A ‘P’ hidden in the middle of a lot of other letters makes it a whole different component. But this one can be soldered both ways. 🙂 ---
**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\ **Post date:** [January 18, 2021, 3:00pm UTC](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727/11 "2021-01-18T15:00:03Z")
> [@eric](#): > > But this one can be soldered both ways. 🙂 That’s my kind of IC. Wonder if I can design an entire synth using no chips but BC847BDW1. And no diodes. ---
**Author:** ![eric](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@eric](https://lookmumnocomputer.discourse.group/u/eric)\ **Post date:** [January 18, 2021, 3:06pm UTC](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727/12 "2021-01-18T15:06:24Z")
Nice challenge 🙂 Most SMD dual diodes come in SOT23 packages, which is assymetrical and can’t be soldered in the wrong orientation. ---
**Author:** ![GhostBassist](https://avatars.discourse-cdn.com/v4/letter/g/b3f665/32.png) [@GhostBassist](https://lookmumnocomputer.discourse.group/u/GhostBassist)\ **Post date:** [January 18, 2021, 4:34pm UTC](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727/13 "2021-01-18T16:34:34Z")
> [@eric](#): > > which is assymetrical and can’t be soldered in the wrong orientation. Challenge accepted 🤣 ---
**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\ **Post date:** [January 18, 2021, 4:44pm UTC](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727/14 "2021-01-18T16:44:13Z")
It can be done if you just flip it through four dimensions! ---
**Author:** ![popflier](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/popflier/32/80_2.png) [@popflier](https://lookmumnocomputer.discourse.group/u/popflier)\ **Post date:** [January 18, 2021, 7:30pm UTC](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727/15 "2021-01-18T19:30:59Z")
Oh, I love that site! Thanks for the link. I really like how they display the information on components. Easy for me to understand. I think I matched an 847 component to the datasheet for the 547. I wasn’t sure if it needed to be single or dual. I didn’t see that listed on the datasheet but maybe I missed it. Is this a good substitute? [https://www.mouser.com/ProductDetail/Nexperia/BC847A215/?qs=me8TqzrmIYWs%2BnVWW1nAcg%3D%3D](https://www.mouser.com/ProductDetail/Nexperia/BC847A215/?qs=me8TqzrmIYWs%252BnVWW1nAcg%3D%3D) I might try your suggestion too @eric and have both to see what works. I also have some of these on hand that I could try since they are in the same package as the 847 I listed above, yes? [MMBT3904LT1G](https://www.mouser.com/ProductDetail/ON-Semiconductor/MMBT3904LT1G/?qs=HVbQlW5zcXUYZ2Fy0YF3FQ%3D%3D) ---
**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\ **Post date:** [January 18, 2021, 7:36pm UTC](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727/16 "2021-01-18T19:36:46Z")
The 847 you link is a single transistor. You can tell because the package has only three legs. So you could use two of them (if your module is a dual gate to trigger like CTorp’s), or one of the one I mentioned. Or two of the MMBT3904LT1G and I’d be shocked if they didn’t work. ---
**Author:** ![popflier](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/popflier/32/80_2.png) [@popflier](https://lookmumnocomputer.discourse.group/u/popflier)\ **Post date:** [January 18, 2021, 7:57pm UTC](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727/17 "2021-01-18T19:57:28Z")
So like this on the schematic? ![Screenshot 2021-01-18 12.54.28](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/d/d998e0dea83ec64e815e6bab4af23b6583dbe237.png) ---
**Author:** ![eric](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@eric](https://lookmumnocomputer.discourse.group/u/eric)\ **Post date:** [January 18, 2021, 8:21pm UTC](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727/18 "2021-01-18T20:21:25Z")
That looks fine to me. ---
**Author:** ![eric](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@eric](https://lookmumnocomputer.discourse.group/u/eric)\ **Post date:** [January 18, 2021, 8:37pm UTC](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727/19 "2021-01-18T20:37:16Z")
You should be breadboarding it first. I’m quite sure connecting the LEDs like this (in the bottom part) will work: ![Screenshot 2021-01-18 12](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/2X/e/eba534ec43fb54c3b5083fc15499f1a53e4e923d.jpeg) And you’ll confirm at the same time the 2N3904 (or MMBT3904) will work. Adjust the 470R ! Probably more like 1K2 or even 2K… ---
**Author:** ![popflier](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/popflier/32/80_2.png) [@popflier](https://lookmumnocomputer.discourse.group/u/popflier)\ **Post date:** [January 19, 2021, 4:46am UTC](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727/20 "2021-01-19T04:46:22Z")
So the only thing that I have changed from @CTorp orig > **Summary** > > This text will be hidden inal K25 module is this transistor. (Well, I also changed the jacks to 3.5mm.) Shouldn’t the rest of the schematic be fine since Cory tested it or are you saying that by changing the transistor that everything that comes after that in the schematic could be affected (i.e…the LED’s, resistors, etc…) ? EDIT: @eric I just NOW realized that you had made a change to the schematic and removed the other pinouts on the tl072 on the lower right portion of the circuit. I didn’t see it at first and thought that you were saying that there was an issue with Cory’s. Sorry for misunderstanding. [Next page](https://lookmumnocomputer.discourse.group/t/smd-equivalent-for-bc547/2727.md?page=2)