Reference sheet
Transistor hFE
Gain and ratings for the jellybean BJTs, lead order included
Transistor current gain (hFE) reference
hFE = Ic / Ib — varies a lot between individual units of the same part, and with temperature and current, so it's quoted at one stated Ic, never as a single flat number. Never design right at the edge of what a minimum hFE allows. hFE alone rarely decides anything, though: what a bench actually needs is "can it take my load" (Ic/Vce/Ptot) and "which leg is the base" — lead order is the classic beginner trap, since it is NOT the same across every jellybean part in the same TO-92 package.
| Part | Type | hFE | Ic max | Vce max | Ptot | Package | Lead order |
|---|---|---|---|---|---|---|---|
| BC547 | NPN | 110 – 800 @ Ic=2mA | 100 mA | 45 V | 500 mW | TO-92 | C-B-E |
| BC557 | PNP | 110 – 800 @ Ic=2mA | 100 mA | 45 V | 500 mW | TO-92 | C-B-E |
| BC337 | NPN | 100 – 630 @ Ic=100mA | 800 mA | 45 V | 625 mW | TO-92 | C-B-E |
| BC327 | PNP | 100 – 600 @ Ic=100mA | 800 mA | 45 V | 625 mW | TO-92 | C-B-E |
| 2N3904 | NPN | 100 @ Ic=10mA (40 – 300 across the full Ic range) | 200 mA | 40 V | 625 mW | TO-92 | E-B-C |
| 2N3906 | PNP | 100 @ Ic=10mA (mirrors the 2N3904) | 200 mA | 40 V | 625 mW | TO-92 | E-B-C |
| 2N2222 (as PN2222A, the common TO-92 version) | NPN | 100 – 300 @ Ic=150mA | 600 mA | 40 V | 625 mW | TO-92 | E-B-C — but confirm against the exact datasheet: the ORIGINAL 2N2222 is a TO-18 metal can, and TO-92 clones sold under related part numbers (e.g. P2N2222A) can be C-B-E instead |
| 2N2907 (as PN2907A, the common TO-92 version) | PNP | 100 – 300 @ Ic=150mA | 600 mA | 60 V | 625 mW | TO-92 | E-B-C — same manufacturer-dependent caveat as the 2N2222 above |
| TIP120 | NPN Darlington | 1,000+ @ Ic=3A (two stages multiply gain) | 5 A | 60 V | 65 W | TO-220 | B-C-E (collector is the metal tab) |
| TIP125 | PNP Darlington | 1,000+ @ Ic=3A (mirrors the TIP120) | 5 A | 60 V | 65 W | TO-220 | B-C-E (collector is the metal tab) |
| S8050 | NPN | 120 – 350 @ Ic=50mA | 700 mA | 25 V | ~0.3–0.625 W (varies by maker) | TO-92 | E-B-C |
| S8550 | PNP | 100 – 300 @ Ic=100mA | 500 mA | 25 V | ~0.3–0.625 W (varies by maker) | TO-92 | E-B-C |
