Dear forum.
I'm working on the "futile" project of a discrete opamp 😉
I'm looking for a good list of currently available SMD BJT transistors.
I was starting out with BC860C / BC850C, which overall I would guess is a good option, with low noise and good linearity.
I'm working on 3 stages; input, VAS/gain, and emitter follower/buffer.
I want to end with a design with relatively low overall distortion, but more important which is predominantly 2. order.
I'm pretty far with the design (LTSpice), but would like to tweak further, with choice of transistors in the different stages.
Input and VAS is PNP, buffer output is push pull NPN/PNP
Does anyone have a good short list to use?
Thanks 🙂
I'm working on the "futile" project of a discrete opamp 😉
I'm looking for a good list of currently available SMD BJT transistors.
I was starting out with BC860C / BC850C, which overall I would guess is a good option, with low noise and good linearity.
I'm working on 3 stages; input, VAS/gain, and emitter follower/buffer.
I want to end with a design with relatively low overall distortion, but more important which is predominantly 2. order.
I'm pretty far with the design (LTSpice), but would like to tweak further, with choice of transistors in the different stages.
Input and VAS is PNP, buffer output is push pull NPN/PNP
Does anyone have a good short list to use?
Thanks 🙂
For some applications you may want dual matched transistors like BC847BS / BC857BS from Nexperia. Good for LTP and current mirrors for example.
Also the BC847BPN (NPN / PNP in one package) seems very useful because both transistors are somewhat thermally coupled inside the same package. Good for Diamond Buffers for example.
Also the BC847BPN (NPN / PNP in one package) seems very useful because both transistors are somewhat thermally coupled inside the same package. Good for Diamond Buffers for example.
Good point Lee with the dual package, to keep size down.
Still missing a good list of different transistors 😉
Still missing a good list of different transistors 😉
Here is a filtered list of transistors from the Toshiba website that may be of interest:
Toshiba SMD BJT Transistors Filtered Table
edit: added LTspice model availability column to the table
Toshiba SMD BJT Transistors Filtered Table
edit: added LTspice model availability column to the table
Last edited:
If you are interested in space saving mainly, the dual transistors of the BC series are also available non-matched for roughly half the cost.
The Toshiba parts seem nice: Low noise, good hFE linearity, complimentary ones available.
But can you actually buy any of the Toshiba parts anywhere?
All Toshiba dual transistors in the filtered list seem to have joined emitters, which makes them less useful since this forfeits the option for emitter degeneration.
Of course you can make up a long wish list of nice parts well suited for such applications, but nowadays sourcing anything has become a challenge.
Better focus on designing your circuit in a way it works well with a variety of whatever you can buy actually.
I've been in your position only a few weeks ago and frustrated when I realized that the market is rather small. And I was pleased to find out that matched transistors are that cheap in SMD.
The Toshiba parts seem nice: Low noise, good hFE linearity, complimentary ones available.
But can you actually buy any of the Toshiba parts anywhere?
All Toshiba dual transistors in the filtered list seem to have joined emitters, which makes them less useful since this forfeits the option for emitter degeneration.
Of course you can make up a long wish list of nice parts well suited for such applications, but nowadays sourcing anything has become a challenge.
Better focus on designing your circuit in a way it works well with a variety of whatever you can buy actually.
I've been in your position only a few weeks ago and frustrated when I realized that the market is rather small. And I was pleased to find out that matched transistors are that cheap in SMD.
I am not sure why you are having difficulty finding what you need. Did you use the search engines at Mouser or Digi-Key?
I can see in some cases it’s difficult because of the way they name packages, for instance sot-23 vs sc-70 vs super-mini vs to-236 etc all basically the same
Here’s one for you
Ksa992: to-92
Fjv992: sot-23
Fjx992: sot-323
I can see in some cases it’s difficult because of the way they name packages, for instance sot-23 vs sc-70 vs super-mini vs to-236 etc all basically the same
Here’s one for you
Ksa992: to-92
Fjv992: sot-23
Fjx992: sot-323
Thanks both 🙂
Overall it seems the "European/American" transistors like BC, 2N etc are easier to get then the Japanese 2SS, 2SK ...
But some of the older but still very good types are obsolete or/and can not be had in SMD
That why I wanted a kind of list of good parts which is readily available, and maybe I should also add; not expensive 😉
BC847/BC857/BC850/BC860 etc are of course more or less universal and can give good results.
Besides the list on Toshiba I have found:
MMBT2222 (2N2222)
MMBT5087 (2N5087) low noise, very linear hfe
Was also looking for a good njf for the input. I think PN4393 (MMBF4393) is a really good and cheap choice.
Alternatives are:
2SK209
2SK170
A modern type is JFE150, but it's 3€ a piece :|
But I'm not really sure the spice model available for PN4393 is right, because DC wise it seems to act different to e.g. 2SK170, 2SK209, and others .....
Overall it seems the "European/American" transistors like BC, 2N etc are easier to get then the Japanese 2SS, 2SK ...
But some of the older but still very good types are obsolete or/and can not be had in SMD
That why I wanted a kind of list of good parts which is readily available, and maybe I should also add; not expensive 😉
BC847/BC857/BC850/BC860 etc are of course more or less universal and can give good results.
Besides the list on Toshiba I have found:
MMBT2222 (2N2222)
MMBT5087 (2N5087) low noise, very linear hfe
Was also looking for a good njf for the input. I think PN4393 (MMBF4393) is a really good and cheap choice.
Alternatives are:
2SK209
2SK170
A modern type is JFE150, but it's 3€ a piece :|
But I'm not really sure the spice model available for PN4393 is right, because DC wise it seems to act different to e.g. 2SK170, 2SK209, and others .....
If someone looks for a cheap, well-matched, reasonably-low-base-resistance dual NPN transistor, I can recommend the BCM56DS.
Some time ago I looked for dual transistors for a low-noise bandgap voltage reference. After looking through dozens of datasheets, I ended up with BCM56DS and NST45011MW6T1G. The NST45011MW6T1G has some information about noise in its datasheet, the BCM56DS has not, but as it is a medium-power dual transistor, I thought there was a good chance it might have a low base resistance. I reserved space for both on my PCB, with zero ohm resistors so I could try what would work best.
I actually couldn't get the NST45011MW6T1G's because they were out of stock, so I built the circuit with the BCM56DS's. The noise I measured was less than what I had calculated for the NST45011MW6T1G's.
When you need single transistors that can handle a bit more power than BC85* and BC86*, the BCP51...BCP56 may be interesting.
Some time ago I looked for dual transistors for a low-noise bandgap voltage reference. After looking through dozens of datasheets, I ended up with BCM56DS and NST45011MW6T1G. The NST45011MW6T1G has some information about noise in its datasheet, the BCM56DS has not, but as it is a medium-power dual transistor, I thought there was a good chance it might have a low base resistance. I reserved space for both on my PCB, with zero ohm resistors so I could try what would work best.
I actually couldn't get the NST45011MW6T1G's because they were out of stock, so I built the circuit with the BCM56DS's. The noise I measured was less than what I had calculated for the NST45011MW6T1G's.
When you need single transistors that can handle a bit more power than BC85* and BC86*, the BCP51...BCP56 may be interesting.
Thanks Marcelvdg
Found the spice model at nexpiria, but it's a .subckt model with no symbol.
Tried the auto generate symbol in LTSpice (for the first time), but I'm uncertain on the pin configuration.
The model states " .SUBCKT BCM56DS 1 2 3 "
1 = b
2 = c
3 = e
????
Does not seem so as it does not really work 😉
Something new to learn 🙂
Found the spice model at nexpiria, but it's a .subckt model with no symbol.
Tried the auto generate symbol in LTSpice (for the first time), but I'm uncertain on the pin configuration.
The model states " .SUBCKT BCM56DS 1 2 3 "
1 = b
2 = c
3 = e
????
Does not seem so as it does not really work 😉
Something new to learn 🙂
That corporation has some "audio" matched 2/4 transistors in SMD packages https://thatcorp.com/that-300-series-low-noise-matched-transistor-arrays/.
Tried to change from BC557C to BCM53DS, with a similar but still bit worse THD result (this was in the second gain stage).
Same for input stage where BC860C seems the right choice.
Tried both BSN53/BSM56 and BCP51/BCP54 for the output buffer and likewise a similar but little worse.
Seems the old BC models are holding up quite well 🙂
.... might be different in other circuits of course 😉
Same for input stage where BC860C seems the right choice.
Tried both BSN53/BSM56 and BCP51/BCP54 for the output buffer and likewise a similar but little worse.
Seems the old BC models are holding up quite well 🙂
.... might be different in other circuits of course 😉
I am looking for a replacement for the BC560 to be used in a power supply that is going to be made SMD, not my design, but I made some modifications based on available parts and the a prior post on the forum. I have checked the BC847BS / BC857BS but I am concerned about the low power handling. As a placeholder for the design I used the 9015, something similar in specs to to the 560 but with a lower power rating. This was what I could find in JLCPOCB, not the optima choice. I need to use a SMD since this is a test project to learn SMD automated manufacturing. Given the low noise of the DC560 I was looking for something that would not increase the noise too much. This is the design and Board. ( input and output caps are also 50V, another change from the original design)
