Electronics > Beginners
Jellybean hobbyist general purpose transistors..
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Zero999:
If you want low cost, then the BC327 and BC547 with no prefix will be cheapest but the gain is pot luck.

Use the BC327 & BC337 for switches. The Hfe is specified with VCE = 1V, which is low enough for most applications.

Use the BC547 & BC557 for linear amplifiers. They have a higher bandwidth than the BC327 & BC337 and I believe are lower noise too.
David Hess:

--- Quote from: Hero999 on October 13, 2017, 08:32:47 am ---
--- Quote from: jaromir on October 13, 2017, 04:41:04 am ---
--- Quote from: Vtile on October 12, 2017, 11:28:44 pm ---BC547B(npn) & BC557B(pnp) comes to my mind.
--- End quote ---

I tend to use BC327/337, as those have higher Ic (800mA versus 100mA), being more useful for switching loads like relays or common anode/cathode of MUX-ed displays.
--- End quote ---

The BC547 & BC557 have a higher current gain than the BC327 & BC227. I like to get the BC547C and BC557C because they have a high beta and aren't much more expensive than the B variants.
--- End quote ---

The BC547/BC557 have higher current gain at lower collector currents, much lower collector currents.  Where they are useful is low input bias and low collector current amplifiers where the input impedance is higher.  The 2N equivalents are the 2N5087/2N5089 which are designed to operate at an even lower current.  You can identify transistors like these by the test current used for their hfe and noise specifications:

BC639/BC640 - 150mA Test Current
2N4401/2N4403 - 150mA Test Current
BC227/BC327 - 100mA Test Current
2N3904/2N3906 - 10mA Test Current
BC547/BC557 - 200uA Test Current (from noise figure)
2N5087/2N5089 - 100uA Test Current

If I was doing low level audio work or building log/antilog amplifiers, then I would add the BC547/BC557 or 2N5087/2N5089 to my list of jelly bean parts.


--- Quote from: Hero999 on October 13, 2017, 12:37:59 pm ---Use the BC547 & BC557 for linear amplifiers. They have a higher bandwidth than the BC327 & BC337 and I believe are lower noise too.
--- End quote ---

The BC547/BC557 have lower current noise at low collector currents so may be used in higher impedance circuits.  The BC327/BC337 would be more appropriate in low impedance circuits where voltage noise needs to be lower at the expense of current noise although they were intended as output drivers.
Vtile:
Thanks..

Now I can navigate in this transistor jungle much easier.

These coding methods started to hunt me, here is a simple explanation for Bxxxx types.

http://www.audiobr.com.br/old/forum/kb.php_mode=article&k=267.html
or
http://www.radio-electronics.com/info/data/semicond/bipolar-transistor-bjt/numbering-codes.php

--- Quote ---ProElectron Coding

An Introduction.     

Once upon a time, long ago, British and European transistors were commonly coded as valves: 0 = no heater, C = triode. However it was quickly realised that everything would end up as an OC something or other (likewise with diodes, which would all become OAxx) and could be confused with existing cold-cathode valve types. So the ProElectron organisation developed a new system of coding semiconductor devices and the one in use today. Basically, British and European transistors are issued with a unique combination of letters and numbers.

The first letter identifies the semiconductor type:

· A = Germanium
· B = Silicon
· C = Gallium Arsenide
· D = other compound semiconductor material

The second letter indicates the intended use:

· A = Small signal diode
· B = Varicap diode
· C = Small signal LF transistor
· D = LF power transistor
· E = Tunnel (Ersaki) diode
· F = RF small signal transistor
· K = Hall effect device
· L = RF power device
· N = Optocoupler
· P = Radiation sensitive device (e.g photo transistor)
· Q = Radiation emitting device (e.g LED)
· R = Low power SCR
· T = High power SCR or triac
· U = High voltage switching transistor
· Y = Rectifier diode
· Z = Zener diode
--- End quote ---
So the European system actually have some information coded in, compared to JEDEC 2Nxxxx codes.
T3sl4co1l:

--- Quote from: David Hess on October 13, 2017, 05:54:49 am ---the 150 volt 2N5401 and 2N5551 would be more suitable.
--- End quote ---

Or the similar MPSA46, or whatever they are, from that family.  MJE350 and complement are also quite popular for audio (driver stage), though the datasheet is sorely wanting.  I think On Semi makes a detailed datasheet?  Or, there are equivalent parts with good data out there, shop around.


--- Quote ---I agree with T3sl4co1l's commendation for the MPSH10/MPSH81 and MMBTH10/MMBTH81 as faster TO-92 and surface mount parts.  Just do not expect RF transistors to perform well as fast saturated switches in switching applications.
--- End quote ---

Also, beware of oscillation, especially as you go over fT > 1GHz.  Keep ferrite beads handy for use on the base or emitter pin. :)


--- Quote ---Get a small signal schottky diode like the 1N5711, BAT41, or BAT83 for use in baker clamps if you want to improve switching.  The BAT41 with its 100mA current rating can do double duty in low current switching regulators.
--- End quote ---

I'm partial to BAT85 and BAT54 (especially BAT54S, handy ESD clamp for logic I/O!), but they're all fine.

And BAV99 for analog / low leakage ESD clamping.

UF4004/7 for fast, higher voltage diodes, or SiC schottky for higher current and high speed, or Si schottky for low voltage and high speed.  Protip: junction diodes are good for snubbers as they have lower capacitance.  The forward recovery voltage (and thus peak voltage overshoot) isn't usually a problem in such application, but the capacitance is.


--- Quote ---There are too many MOSFET options for me to make a good recommendation.  The problem with many of them is marginal switching on 3.3 or even 5 volts; the true logic level ones are more expensive.

--- End quote ---

FWIW, this is physics: MOSFETs rated 30V and up are physically different from those below.  The Rds(on) tempco is large (usually 1.8-2.5 times higher at 150/175C than at 25C), and the gate threshold and turn-on-ness (i.e., transconductance) isn't very good.  You can always adjust threshold (from negative Vgs(th) depletion mode, to enhancement with Vgs(th) up to 5V), but you can't adjust the slope of how fast it turns on.  Point being, you can get "logic level" power FETs, with Vgs(th) around 0.8V, and they're usable at 5V drive, but they still turn on harder if drive is stepped up to 9V, say.  They're also very slow at 5V, because drive current is limited by series resistance.

Devices 20V and under, however, have a shallower Rds(on) curve, and much more transconductance.  12V devices are effective at 2.5V logic level and below.  There's one part out there with Rds(on) in the microohms (for battery management)!

So if you have an application that's on the borderline between choosing 20 and 30V devices, try to use 20V.  To keep the circuit safe, put more effort into controlling peak voltages (add snubbers, use slower commutation, or a resonant design).

Tim
orolo:

--- Quote from: Hero999 on October 13, 2017, 08:32:47 am ---The BC547 & BC557 have a higher current gain than the BC327 & BC227. I like to get the BC547C and BC557C because they have a high beta and aren't much more expensive than the B variants.

--- End quote ---
I also stock the C series for the same reason, and the 'low noise, higher voltage' 550/560s since there is no great price difference.

But there is a catch, that I first heard of from Bob Pease: the higher the beta, the lower the output impedance. It can be seen in this datasheet: the 547A has 55.5k typical output impedance, the 547B 33.3k, and the 547C 16.6k, and it could go as low as 9k!. This can be very important when building current sources/sinks, active loads, etc. The beta-output impedance relationship seems to be (rougly) inversely proportional. This has led me to think seriously about stocking low beta versions of the transistor.

The Vishay datasheet for the PNP parts quotes the same output impedances for the A,B,C series. IIRC, in the Art of Electronics, data suggested that PNP parts often have even lower output impedance (lower Early voltage).
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