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TO-92 · 2N3904
ActiveNPN General-Purpose BJT
2N3904
onsemi · TO-92 · NPN General-Purpose BJT
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Overview
The 2N3904 is the industry-standard NPN small-signal transistor, and the onsemi TO-92 version is the part most engineers reach for first when a circuit needs amplification or switching below 200mA. It is rated 40V collector-emitter, 60V collector-base and 6.0V emitter-base, with 200mA continuous collector current and 625mW of dissipation at TA = 25°C.
DC current gain is 100 to 300 at IC = 10mA and VCE = 1.0V, with a guaranteed minimum of 30 even at 100mA, and saturation voltage of 0.2V maximum at IC = 10mA with IB = 1mA. The 300MHz gain-bandwidth product, 4.0pF output capacitance and 8.0pF input capacitance make it comfortable in RF front ends, oscillator circuits and switching applications into the low megahertz.
The 2N3904 and its PNP complement 2N3906 form the classic complementary pair used in push-pull output stages, level shifters and differential inputs. The device is second-sourced by onsemi, STMicroelectronics, Diodes Inc, Central Semiconductor and dozens of Asian vendors, which keeps price near a few cents in volume but also makes remarked and low-gain clones common. Verify hFE at 10mA and VCE(sat) at 10mA/1mA on incoming inspection. Pinout is emitter-base-collector. Shenzhen stock is abundant, MOQ 2,000 pcs on tape or 1,000 pcs bulk.
Key Features
- 40V / 200mA NPN small-signal transistor in TO-92
- hFE 100-300 at IC = 10mA, VCE = 1.0V
- VCE(sat) 0.2V max at 10mA - clean low-level switching
- 300MHz fT suits RF and fast switching
- Complementary pair with 2N3906
Typical Applications
- General-purpose small-signal amplification
- Low-current switching from MCU GPIOs
- Push-pull and complementary stages with 2N3906
- Oscillators, RF front ends and mixer stages
- Level shifting and open-collector interfacing
- Current mirrors and current-source circuits
Specifications
- Polarity / Channel Type
- NPN
- Collector-Emitter Voltage (VCEO)
- 40 V
- Collector-Base Voltage (VCBO)
- 60 V
- Continuous Collector Current (IC)
- 200 mA
- DC Current Gain hFE (IC = 10 mA, VCE = 1.0 V)
- 100 to 300
- VCE(sat) max (IC = 10 mA, IB = 1.0 mA)
- 0.2 V
- Gain-Bandwidth Product (fT)
- 300 MHz
- Power Dissipation (PD, TA = 25 °C)
- 625 mW
- Pins
- 3
- RoHS
- Compliant
Procurement Tips
Buy the 2N3904 in tape-and-reel for SMT-adjacent hand assembly lines and keep a qualified second source (for example Diodes Inc or ST) on the AVL; the part is cheap enough that counterfeit risk, not price, should drive your sourcing decision.
Frequently Asked Questions
2N3904 vs 2N2222 / PN2222A - what is the real difference?
Same NPN concept, different current class. 2N3904 is a 200mA small-signal part optimized for gain and frequency; PN2222A is a 600mA switch with better high-current gain but slightly lower fT. Use 2N3904 for signal work under 100mA and PN2222A for relay and lamp loads.
2N3904 vs BC547 - can I substitute?
Broadly yes for low-current work, but pinouts differ: 2N3904 TO-92 is emitter-base-collector while BC547 is commonly collector-base-emitter. Ratings also differ (BC547 is 45V/100mA with higher gain bands). Always re-check pinout and gain band before substituting on an existing layout.
What base resistor do I use to switch a 50mA load from 3.3V?
For saturation use a forced beta of 10, so 5mA of base current. From 3.3V with VBE about 0.7V that is (3.3-0.7)/0.005 = 520Ω; use 470Ω. The datasheet guarantees VCE(sat) of 0.3V max at IC = 50mA with IB = 5mA, confirming this drive level.
Can the 2N3904 handle 24V loads?
Yes for voltage: VCEO is 40V so a 24V rail leaves margin. Watch inductive kickback from relays or solenoids, which can exceed 40V without a flyback diode; add a 1N4148 or 1N4007 across the coil.
How do I verify a genuine 2N3904?
Measure hFE at IC = 10mA, VCE = 1.0V (genuine reads 100-300) and VCE(sat) at 10mA/1mA (under 0.2V). Check the laser or ink marking, matte-tin leads and consistent TO-92 weight. Clones often show hFE below 60 or high leakage. We sample-test each reel.
What is the MOQ and lead time?
MOQ is 2,000 pcs on tape-and-reel or 1,000 pcs bulk for onsemi 2N3904; 100 pcs loose for prototypes. Shenzhen stock ships in 1-2 days; authorized replenishment is 8-14 weeks.
Alternatives & Equivalents
MMBT3904
onsemi
equivalent
PN2222A
onsemi
alternative
2N3906
onsemi
companion
S8050
Diodes Incorporated
alternative
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