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| Number | Type | Style | Vbe(sat) | Vce(sat) | hFE | Vceo | Vcbo | Vebo | Vce(max) | Vcb(max) | Vbe(max) | Ic(max)Ic max | Data Sheet |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| BC337 | NPN | CBE | 1.2v | 0.7v | 100 (@100mA) | 45v | 50v | 5v | 800 mA | https://www.onsemi.com/pub/Collateral/BC337-D.PDF | |||
| BC327 | PNP | CBE | -45v | -5v | -800mA | ||||||||
| 2N2222 | NPN | EBC | 30v | 60v | 5v | 800mA | |||||||
| 2N2907 | PNP | EBC | -40v | -60v | -5v | -600mA | |||||||
| 2N3904 | NPN | EBC | 40v | 60v | 6v | 200mA | |||||||
| 2N3906 | PNP | EBC | -40v | -40v | -5v | 200mA | |||||||
| S8050 | NPN | EBC | 20v | 30v | 5v | 700mA | |||||||
| S8550 | PNP | EBC | -25v | -40v | -5v | -700mA | |||||||
| C1815 | NPN | EBC | 50v | 60v | 5v | 150mA | |||||||
| A1015 | PNP | EBC | -50v | -50v | -150mA | ||||||||
| S9013 | NPN | EBC | 25v | 45v | 5v | 500mA | |||||||
| S9012 | PNP | EBC | 25v | 40v | 5v | -500mA | |||||||
| S9014 | NPN | EBC | 45v | 50v | 5v | 100mA |
...
| Style | |
|---|---|
| EBC |
|
| CBE | Collector, Base, Emitter |
Calculating your Rb Value
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Ic = Vcc/RL = 12v/155Ω = 78mA
Vb = 3.3v - Vbe(sat) = 3.3 - 1.2 = 2.1v
Calculating using Ib=Ic/10
It is common to assume that base current is 1/10 of the collector current.
Ib = Ic/10 = 78/10 = 7.8mA
Rb = Vb/Ib = 2.1/0.0078 = 269 Ω
Tested with 220 Ω and it worked.
Calculating using hFE
To guarantee that the transistor operates in the saturation region, we multiply the base current by a factor of three.
hFE=100 (@100mA)
Ib = Ic/Hfe = 78/100 = 0.78mA
Rb = Vb/Ibx3 = 2.1/(0.00078x3) = 897 Ω
Calculating using the online calculator
See reference
hFE=100
Rb = 960 Ω
Why are these all so different??? I gues it would work from 200 to 1KΩ.
References
| Reference | URL |
|---|---|
| Base Resistor Calculator | https://www.petervis.com/GCSE_Design_and_Technology_Electronic_Products/transistor_base_resistor_calculator/transistor_base_resistor_calculator.html |