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WIP: my attempt at a list of "common transistors" with regions and explanations

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JLNY

Active Member
Hello all,

A bit of background: I was recently watching a video online describing a circuit which used discrete transistors. The individual making the video was an engineer from Scotland, so all of his circuits were based around the BC-family of transistors commonly used in the UK, which I tend to be less familiar with. This got me thinking about all of the various transistors that are used as "go-to" transistors by hobbyists.

There are plenty of lists online of "common transistors" that recommend what type of transistors to keep on hand, but very few try to give details as to why they are used or how people choose to apply them. This can be especially confusing when different parts of the world have different conventions for which transistor types they use, so I thought I would try to compile my own list of "common transistors" and then try to give some of the reasoning and ways in which they are used so that new hobbyists or hobbyists from other countries could get a better sense of the applications for a particular transistor.

For each transistor, I give a brief summary of how I have typically seen them used. For NPN BJTs or N-channel FETs, I also list its matching PNP or P-channel complement if it has one (in parentheses). Naturally, there are going to be MANY exceptions for all of these, but I think it can be useful to just give the broad strokes on how hobbyists generally use them. There is probably a lot of overlap between regions where a particular value is used in many places, so for the moment I have only broken the small signal BJTs into seperate regions.

tl;dr: I am looking for community input here, so feel free to suggest changes, corrections, or submit your own transistors to the list with descriptions. That said, I am mainly looking to just cover the major hobbyist "staples" rather than list every single transistor, so try to keep it to transistors that you have seen used by multiple people across many designs. I'm looking to avoid just listing tech specs and instead give general descriptions and typical applications.

I dunno, does this seem like a useful direction to pursue that could be used as a reference for people? I would be curious to see what people have to say about the various families and why certain values are preferred over others.

[Purple text in brackets will be used to mark comments and areas that I would like to improve.]

Small signal BJT (TO-92):

US/Canada:
  • 2N3904 (complement: 2N3906): often used for its high gain as an amplifier in low-current applications. Its small signal gain is highest in the 10mA region. Its high frequency range also allows it to be used in some RF applications.
  • 2N4401 (complement: 2N4403): Has better gain at high current than 2N3904. It is generally used for medium current and switching applications in the 100mA range.
  • 2N2222, PN2222 (complement: 2N2907): Considered to be a good compromise between 2N3904 and 2N4401. It is often used as a kind of generic transistor in applications where “any old transistor” will usually work. Also has a higher voltage “A” variant (e.g. 2N2222A).

UK/Europe [may need to be broken into two or more regions?]:
  • BC546, BC547, BC548 (complement: BC556, BC557, BC558): [need descriptions from someone familiar with these families]
  • BC337, BC338 (complement: BC327, BC328):
  • BC182, 183, 184 (BC212, BC213, BC214):
Other regions:

[I see the Japanese "2S" family used on many designs, but I'm not sure if they are particular to any countries/regions or what values are considered the most common to use.]


Small signal FET (TO-92):
  • 2N7000: used as a general purpose enhancement mode MOSFET. Has a relatively high transconductance for a small signal FET.
  • MPF102: although discontinued, this high frequency JFET has been a staple in amateur radio for RF oscillator circuits. With no direct replacement, this part is still sometimes used in newer designs. [there may be inaccurate info here. If HAMs have started adopting a replacement, let me know what it is so I can list it]

Power BJT:
  • 2N3055 (complement: MJ2955): a TO-3 package power BJT often used as a class AB pair in audio power amplifiers.
  • TIP31, TIP41 (complement: TIP32, TIP42): a TO-220 package power BJT used in switching applications. Has moderate gain at high current. Also has higher voltage “A,” “B,” and “C,” variants (e.g. TIP31C).
  • TIP100/1/2 (e.g. TIP102), TIP120/1/2 (complement: TIP105/6/7, TIP125/6/7): a TO-220 package Darlington pair power transistor often used for switching applications. Popular with microcontroller enthusiasts for being easily driven by logic-level signals with a resistor in series with the base.
  • MJE340 (complement: MJE350): a medium-power TO-126 package BJT often used in audio amplifiers. often used as buffers to the final power transistors or as a “VBE multiplier” for biasing.
Power FET:
  • IRF510, IRF540, IRF630, and others (complement: IRF9510, IRF9540, IRF9630, etc.) a large family of TO-220 MOSFETs often used in switching applications or in class AB power amplifiers. Higher current “N” variants (e.g. IRF9540N) also exist. [What would be the best approach to the topic of large families like this where many similar parts from the same family are used?]
  • IRF3205 (complement: IRF4905): a TO-220 MOSFET with low on resistance and high current handling capabilities. often used in switching applications and popular with microcontroller enthusiasts as a high current driver.
Awaiting confirmation: [items I have seen mentioned online, but am not sure if they are "common" enough to add to the list. I will add them if I can get confirmation from the community that they have seen them used in multiple designs]
IRF2805: N channel mosfet, switching applications, microcontroller applications
IRF1405: N channel mosfet, switching applications, microcontroller applications
IRF5305: P channel mosfet, switching applications, microcontroller applications
RFP30N06LE, FQP30N06L (complement FQP27P06?): N channel mosfet, switching applications, microcontroller applications

Edit credits:
MikeMI (correction about TIP100-family usage)
DerStrom8 (clarification on P-type complements)
kinarfi (addition of IRF3205, IRF4905, and IRF2805)

Cheers,
JLNY
 
Last edited:

MikeMl

Well-Known Member
Most Helpful Member
On the power FETs: I bought a bunch of NMOS and PMOS logic-gate ones in TO220 packages before they were replaced with SMD parts. The ones you list cannot be driven directly from a 3.3V or 5V microcontroller.
 

alec_t

Well-Known Member
Most Helpful Member
I'm rather surprised that there are currently any regional preferences for transistors (or any other component for that matter). Manufacturing operations nowadays tend to be centred in Asia. National operations have dwindled. Many components are now bought through online retailers/wholesalers, or via multinational companies/distributors, so country of origin is perhaps less important than it once was.
 

JLNY

Active Member
On the power FETs: I bought a bunch of NMOS and PMOS logic-gate ones in TO220 packages before they were replaced with SMD parts. The ones you list cannot be driven directly from a 3.3V or 5V microcontroller.
Good point, generally I have seen them used with a resistor in series with the base. I will edit this to clarify what I meant. A quick search of "TIP122 Arduino" definitely yields results, so for whatever reason, they seem to be commonly used, even if personally they are not necessarily the best choice compared to a MOS device.
 

JLNY

Active Member
I'm rather surprised that there are currently any regional preferences for transistors (or any other component for that matter). Manufacturing operations nowadays tend to be centred in Asia. National operations have dwindled. Many components are now bought through online retailers/wholesalers, or via multinational companies/distributors, so country of origin is perhaps less important than it once was.
I don't disagree with your reasoning, but it seems that old habits die hard. Many hobbyists want others to be able to repeat their designs, so they try to use transistor types that others will be likely to have on hand. Many of these transistors tend to be older designs that have been used by hobbyists for decades, and so the regional preferences for specific part numbers persist even if their country of origin is the same nowadays. That said, the regional component of this is secondary to just giving a typical application description.
 
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DerStrom8

Super Moderator
Most Helpful Member
Hi JLNY,

When you mention "complements" you may want to clarify that you mean they are the PNP versions of the NPN transistors. It may not be clear to people who have not used them before and are not as familiar with how transistors work.
 

JLNY

Active Member
When you mention "complements" you may want to clarify that you mean they are the PNP versions of the NPN transistors. It may not be clear to people who have not used them before and are not as familiar with how transistors work.
Updated. Thanks, I am definitely the type that forgets to curb their technical jargon for others at times.

...For each transistor, I give a brief summary of how I have typically seen them used. For NPN BJTs or N-channel FETs, I also list its matching PNP or P-channel complement if it has one (in parentheses)...
I imagine if there were any P-types without specific N-type complements added to the list, I would probably specifically mention that in the description, but otherwise it can be assumed that most will be N-types.
 
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Tony Stewart

Well-Known Member
Most Helpful Member
The problem with old diehard transistors is the specs are so loose that datasheets don't even show all the imperfections.
So if you can tolerate a 6:1 range on hFE use them, otherwise ROHM always bins their parts with at least 3 tight ranges.
Since they are all 100% tested it is not that hard to have a binning process as they tend to be matched on each wafer.

I do the same on on LED large custom orders and only buy single bin parts with 0.2V bin sizes and 20% tolerance on Iv intensity rather than a 2:1 range or more. When you order in volume you get what you specify and the cost is not much more.


If I were designing for volume production and wanted fewer issues with ATE or functional test tolerances, I would choose devices with the best price /performance ratio. My past experience leaned towards ROHM 's discrete and pre biased switch arrays. This opens up a wide field of other choices in the 2SCxxxx family of parts that cost a few pennies.

e.g. http://rohmfs.rohm.com/en/products/...screte/transistor/bipolar/2sc2412kt146q-e.pdf
 

JLNY

Active Member
The problem with old diehard transistors is the specs are so loose that datasheets don't even show all the imperfections.
So if you can tolerate a 6:1 range on hFE use them, otherwise ROHM always bins their parts with at least 3 tight ranges.
FWIW, I think the BC546/7/8 family are binned for gain in a similar way with "A," "B," and "C" ranges (bottom of page 2): https://www.fairchildsemi.com/datasheets/BC/BC547.pdf

but yeah, that is a problem with many of these really oldschool transistors.
 

JLNY

Active Member
The datasheets these days on old devices don't even have curves was my main point.
ok for those that know what to expect or don't care about thermal effects on linearity etc.

e.g. https://www.fairchildsemi.com/datasheets/PN/PN2222.pdf
Not sure why the curves are missing on that particular datasheet. Try this one: http://web.mit.edu/6.131/www/document/pn2222a.pdf
That's not so much a problem with the transistors as much as just the datasheet.
In most cases, many starting hobbyists generally won't be concerned with thermal effects or linearity. Designs that need high linearity with discrete transistors will probably have feedback to control the gain and use other techniques to compensate for the nonlinear effects of transistors.
 

Tony Stewart

Well-Known Member
Most Helpful Member
Not sure why the curves are missing on that particular datasheet. Try this one: http://web.mit.edu/6.131/www/document/pn2222a.pdf
That's not so much a problem with the transistors as much as just the datasheet.
In most cases, many starting hobbyists generally won't be concerned with thermal effects or linearity. Designs that need high linearity with discrete transistors will probably have feedback to control the gain and use other techniques to compensate for the nonlinear effects of transistors.
The difference is in the dates. Mine was released a few months later in 2004. probably because the nominal curves could not be trusted with loose MFG tolerances.
 

kinarfi

Well-Known Member
Hello all,

A bit of background: I was recently watching a video online describing a circuit which used discrete transistors. The individual making the video was an engineer from Scotland, so all of his circuits were based around the BC-family of transistors commonly used in the UK, which I tend to be less familiar with. This got me thinking about all of the various transistors that are used as "go-to" transistors by hobbyists.

There are plenty of lists online of "common transistors" that recommend what type of transistors to keep on hand, but very few try to give details as to why they are used or how people choose to apply them. This can be especially confusing when different parts of the world have different conventions for which transistor types they use, so I thought I would try to compile my own list of "common transistors" and then try to give some of the reasoning and ways in which they are used so that new hobbyists or hobbyists from other countries could get a better sense of the applications for a particular transistor.

For each transistor, I give a brief summary of how I have typically seen them used. For NPN BJTs or N-channel FETs, I also list its matching PNP or P-channel complement if it has one (in parentheses). Naturally, there are going to be MANY exceptions for all of these, but I think it can be useful to just give the broad strokes on how hobbyists generally use them. There is probably a lot of overlap between regions where a particular value is used in many places, so for the moment I have only broken the small signal BJTs into seperate regions.

tl;dr: I am looking for community input here, so feel free to suggest changes, corrections, or submit your own transistors to the list with descriptions. That said, I am mainly looking to just cover the major hobbyist "staples" rather than list every single transistor, so try to keep it to transistors that you have seen used by multiple people across many designs. I'm looking to avoid just listing tech specs and instead give general descriptions and typical applications.

I dunno, does this seem like a useful direction to pursue that could be used as a reference for people? I would be curious to see what people have to say about the various families and why certain values are preferred over others.

[Purple text in brackets will be used to mark comments and areas that I would like to improve.]

Small signal BJT (TO-92):

US/Canada:
  • 2N3904 (complement: 2N3906): often used for its high gain as an amplifier in low-current applications. Its small signal gain is highest in the 10mA region. Its high frequency range also allows it to be used in some RF applications.
  • 2N4401 (complement: 2N4403): Has better gain at high current than 2N3904. It is generally used for medium current and switching applications in the 100mA range.
  • 2N2222, PN2222 (complement: 2N2907): Considered to be a good compromise between 2N3904 and 2N4401. It is often used as a kind of generic transistor in applications where “any old transistor” will usually work. Also has a higher voltage “A” variant (e.g. 2N2222A).

UK/Europe [may need to be broken into two or more regions?]:
  • BC546, BC547, BC548 (complement: BC556, BC557, BC558): [need descriptions from someone familiar with these families]
  • BC337, BC338 (complement: BC327, BC328):
  • BC182, 183, 184 (BC212, BC213, BC214):
Other regions:

[I see the Japanese "2S" family used on many designs, but I'm not sure if they are particular to any countries/regions or what values are considered the most common to use.]


Small signal FET (TO-92):
  • 2N7000: used as a general purpose enhancement mode MOSFET. Has a relatively high transconductance for a small signal FET.
  • MPF102: although discontinued, this high frequency JFET has been a staple in amateur radio for RF oscillator circuits. With no direct replacement, this part is still sometimes used in newer designs. [there may be inaccurate info here. If HAMs have started adopting a replacement, let me know what it is so I can list it]

Power BJT:
  • 2N3055 (complement: MJ2955): a TO-3 package power BJT often used as a class AB pair in audio power amplifiers.
  • TIP31, TIP41 (complement: TIP32, TIP42): a TO-220 package power BJT used in switching applications. Has moderate gain at high current. Also has higher voltage “A,” “B,” and “C,” variants (e.g. TIP31C).
  • TIP100/1/2 (e.g. TIP102), TIP120/1/2 (complement: TIP105/6/7, TIP125/6/7): a TO-220 package Darlington pair power transistor often used for switching applications. Popular with microcontroller enthusiasts for being easily driven by logic-level signals with a resistor in series with the base.
  • MJE340 (complement: MJE350): a medium-power TO-126 package BJT often used in audio amplifiers. often used as buffers to the final power transistors or as a “VBE multiplier” for biasing.
Power FET:
  • IRF530, IRF540, IRF630, and others (complement: IRF9530, IRF9540, IRF9630, etc.) a large family of TO-220 MOSFETs often used in switching applications or in class AB power amplifiers. Higher current “N” variants (e.g. IRF9540N) also exist. [What would be the best approach to the topic of large families like this where many similar parts from the same family are used?]

Edit credits:
MikeMI (correction about TIP100-family usage)
DerStrom8 (clarification on P-type complements)

Cheers,
JLNY
I like it, good idea, my addition would be power FETs IRF3205 and IRF2805 (complement IRF4905)
Thanks,
Jeff
 

JLNY

Active Member
I like it, good idea, my addition would be power FETs IRF3205 and IRF2805 (complement IRF4905)
Thanks,
Jeff
Awesome, glad to hear this might be of use to some folks. What are the typical uses you have seen for these? A quick search seems to indicate that they are mostly used in switching applications, and I see some mention of IRF3205 and IRF4905 in microcontroller applications. The transconductance and current handling seem quite high, but their high input capacitance might make them slightly more difficult to use in some audio applications. I don't see as much documentation on IRF2805, how commonly have you seen that used?

EDIT: IRF3205 and IRF4905 have been added to the list. I have definitely seen those mentioned before. I have also added a list of parts "awaiting confirmation" and added IRF2805 to it.
 
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