Fairchild Semiconductor 2N3904RM
Full Technical Specifications
12 Parameters| Parameter / Attribute | Specification / Value |
|---|---|
| Mounting | Through Hole |
| FET type | NPN |
| Voltage - collector emitter breakdown | 40 V |
| Current - collector (Ic) | 200 mA |
| Current - collector cutoff | 50nA |
| DC current gain (hFE) (Min) @ ic, vce | 100 @ 10mA, 1V |
| Power - max | 625 mW |
| Frequency - transition | 300MHz |
| Operating temperature | -55°C ~ 150°C (TJ) |
| Package | Bulk |
| Case | TO-226-3, TO-92-3 (TO-226AA) Formed Leads |
| Vce saturation (Max) @ ib, ic | 300mV @ 5mA, 50mA |
Need Stock or a Drop-in Second-Source for 2N3904RM?
Package: TO-92 / SOT-23 · Pin-compatible replacements with immediate Shenzhen spot stock
The 2N3904 NPN and its 2N3906 PNP complement are the American small-signal standard: 40V, 200mA, 625mW, TO-92 with E-B-C lead order, gain optimized around 10mA, and SOT-23 twins (MMBT3904 / MMBT3906) in more new designs than the through-hole originals. The repair trap has two layers: the European counterpart BC547 is C-B-E in the same TO-92 body - a straight insertion swaps emitter and collector into reverse-active operation - and the SOT-23 twins number their pins 1 = Base, 2 = Emitter, 3 = Collector, which follows neither lead order. Every substitution in this family answers the pinout question before the electrical one.
Verified Pin-Compatible Replacements (3 verified alternatives)
The European Counterpart, C-B-E Reversed
Shenzhen Spot Stock (24-48h Dispatch)
The functional twin from the other design culture: 45V, 100mA, the same 300MHz-class fT - and the mirrored lead order (C-B-E against E-B-C) that makes the socket, not the spec, the first question.
The same small-signal envelope; the BC547 comes in A/B/C gain groups (110-800 hFE) where the 2N3904 ships one broad 100-300 band.
The Same Pins With Three Times the Muscle
Shenzhen Spot Stock (24-48h Dispatch)
The higher-current sibling in the same E-B-C order and 40V class: 600-800mA against 200mA, gain optimized around 150mA, fT 250-300MHz - the standard step up for relay, LED and small-motor duty.
Same 40V VCEO; the plastic TO-92 version shares this pinout exactly, which is why repair benches stock both in one drawer.
The Quiet 600mA Middle Step
Shenzhen Spot Stock (24-48h Dispatch)
The in-between option of the US lineup: 40V, 600mA, E-B-C order, fT 250MHz - closer to the 2N3904 noise behavior than the 2N2222A, at higher current than the 2N3904.
Same 40V class across the trio.
Buyer & Quality Checklist for Sourcing Alternatives
- The pocket-sized pinout map of small-signal TO-92: American parts (2N3904, 2N3906, 2N2222A plastic) are E-B-C, European parts (BC547, BC337) are C-B-E, and Japanese parts (2SC945, 2SA733) are E-C-B. Three standards, one body - check the flat-face drawing even when the cross-reference list says equivalent.
- The SOT-23 twins renumber: MMBT3904 / MMBT3906 are 1 = Base, 2 = Emitter, 3 = Collector - neither the TO-92 order nor a scaled copy of it. Reflow repairs that swap by remembered position are the same trap in a smaller package.
- Reverse-active operation is the silent failure of a flipped swap: the part conducts and may even pass a diode test, but hFE collapses to a fraction and saturation voltage climbs - a circuit that works but weakly after a transistor change should be re-checked for a rotated emitter and collector.
- Gain groups matter by design culture: BC547 ships as A/B/C bands (110-220 / 200-450 / 420-800) and circuits select them; the 2N3904 ships one 100-300 band. Substituting a selected-band part with a generic one needs the bias network reviewed, not just the socket.
- Current ceilings decide the direction: 2N3904 at 200mA optimized for 10mA, 2N4401 at 600mA, 2N2222A at 600-800mA optimized near 150mA, BC547 at 100mA. Stepping down in a driver that legitimately passed more current is the classic post-repair smoke test failure.
- Keep the cans apart: the metal TO-18 2N2222 (and 2N2907) do not share the plastic E-B-C circle. One drawer label per package, or the next repair inherits the mistake.
Frequently Asked Technical Questions
Q: Can I replace a BC547 with a 2N3904?
A: Electrically they overlap (45V/100mA against 40V/200mA small-signal NPN), but the TO-92 lead orders are mirrored: BC547 is C-B-E and the 2N3904 is E-B-C. A straight insertion runs the part reverse-active with collapsed gain - re-form the leads, or substitute within the same pinout culture.
Q: What is the difference between 2N3904 and 2N2222A?
A: Same E-B-C pinout and 40V class, different current: the 2N3904 carries 200mA with gain optimized near 10mA, the 2N2222A 600-800mA optimized near 150mA. Using the 2222A in a 3904 socket is free headroom; the reverse is safe only inside the 200mA budget.
Q: Why does a transistor work but with terrible gain after a swap?
A: Emitter and collector are most likely exchanged: reverse-active operation conducts at a small fraction of the rated hFE with a higher saturation voltage. Check the flat-face pin drawing of both parts - C-B-E and E-B-C look identical from across the bench.