2N3904TA - 40V NPN GP BJT 200mA | onsemi TO-92
Teilenummer: 2N3904TA ✓ Aktiv| Menge | Stückpreis | Gesamt |
|---|---|---|
| 1 | $0.07 | $0,07 |
| 10 | $0.06 | $0,60 |
| 100 | $0.05 | $5,00 |
| 500 | $0.04 | $20,00 |
| 1.000 | $0.03 | $30,00 |
2N3904TA Übersicht
A bipolar junction transistor (BJT) is a three-terminal semiconductor device made of three doped regions (emitter-base-collector) forming two PN junctions. An NPN BJT turns on when the base is biased above the emitter by approximately 0.7 V; a small base current then controls a much larger collector current. NPN BJTs sit within the broader transistor taxonomy: transistor -> bipolar transistor -> BJT -> NPN BJT, and they are commonly used for low-power linear amplification, switching, and signal conditioning.
Key features include a collector-emitter voltage (VCEO) of 40 V, collector-base voltage (VCBO) of 60 V, emitter-base voltage (VEBO) of 6 V, DC current gain (hFE) of 100 to 300 at 10 mA, and a low collector-emitter saturation voltage (VCE(sat)) of approximately 0.2 V at 10 mA base drive. The TO-92 package offers a typical thermal resistance of 200 C/W (junction-to-ambient), and the device operates across -55 C to +150 C junction temperature.
The 2N3904TA uses an epitaxial planar NPN die construction with a single base contact and a buried layer for improved switching performance. This die is shared across the broader 2N3904 / MMBT3904 / PZT3904 family, and it offers well-characterized SPICE parameters for simulation. The relatively high fT of 300 MHz and good hFE linearity make it work equally well as a low-frequency audio amplifier and as a small-signal switch driving relays, LEDs, or logic-level MOSFET gates.
Typical applications include low-power linear amplifiers, direct-coupled logic level translation, oscillator stages, driver stages for higher-power transistors, and general switching of relays and LEDs in consumer, industrial, and educational designs. The classic complementary PNP counterpart is the 2N3906.
When designing with the 2N3904TA, observe base current drive of roughly 1/10 of the desired collector current for saturated switching operation, and ensure the collector dissipation remains below 625 mW or further derate for elevated ambient temperatures. The TO-92 package dissipates heat primarily through its leads, so use generous copper area on the PCB ground pour if continuous operation near maximum ratings is anticipated.
This page synthesizes distributor pricing, parametric drop-in alternatives (same TO-92 footprint, key parameters within 30%), and practical design notes not found in the bare manufacturer datasheet. It targets engineers evaluating the onsemi 2N3904TA against the original Fairchild 2N3904 and competing through-hole NPN transistors such as the 2N4401 and BC547.
Drop-in-Alternativen für 2N3904TA – gleiches Gehäuse, Pin-kompatibel. Bauteile mit anderem Gehäuse, die eine PCB-Überarbeitung erfordern, sind ausgeschlossen.
Schnellvergleichstool – Wählen Sie Alternativbauteile für den Direktvergleich:
2N3904BU
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
2N3904TAR
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
2N4401TA
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
BC547B
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
P2N2222A
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
PN2222ABU
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
2N3904
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
2N3904TA Grenzwerte & elektrische Eigenschaften
| Transistortyp | NPN Bipolar Junction Transistor |
| Gehäuse | TO-92-3 (TO-226AA), through-hole |
| Kollektor-Emitter-Spannung (Vceo) | 40 V |
| Kollektor-Basis-Spannung (Vcbo) | 60 V |
| Emitter-Basis-Spannung (Vebo) | 6 V |
| Continuous Collector Current (IC) | 200 mA |
| Total Power Dissipation (Pd) | 625 mW |
| DC Current Gain (hFE) | 100 to 300 at IC=10 mA, VCE=1 V |
| Übergangsfrequenz (ft) | 300 MHz (typ) |
| Kollektor-Emitter-Sättigungsspannung (Vce(sat)) | 0.2 V (typ) at IC=10 mA, IB=1 mA |
| Betriebs-Sperrschichttemperatur | -55 C to +150 C |
| Storage Temperature | -55 C to +150 C |
| Thermal Resistance (RthJA) | 200 C/W (typ, datasheet) |
| Montageart | Through Hole |
| Polarity | NPN |
| RoHS-Status | Pb-Free (compliant per onsemi datasheet) |
2N3904TA Pin-Konfiguration
| Pin 1 | Emitter — Current exits the transistor when active; bias ≈ 0.7 V below base |
| Pin 2 | Base — Control terminal; small current here modulates collector current |
| Pin 3 | Collector — Main current terminal; connected to load in common-emitter configuration |
Sicherer Arbeitsbereich (DC, TO-92, 25 C ambient)
Typische Anwendungen
2N3904TA ist geeignet für 6 Anwendungs: Low-power Linear Audio Amplifier Stage, Low-side Relay / Solenoid Driver Switch, Logic-Level Translation (3.3 V to 5 V / 12 V), RF / IF Amplifier Stage up to 100 MHz, Astable / Monostable Multivibrator Timing Circuit, Arduino / Microcontroller General-Purpose Switching.
Low-power Linear Audio Amplifier Stage
The 2N3904TA fits small-signal audio amplifier stages because its 40 V VCEO easily handles common 9 V and 12 V supply rails, its 300 MHz fT preserves bandwidth well above the audio band, and its hFE of 100-300 at 10 mA delivers predictable voltage gain in common-emitter topologies. A typical preamp stage uses an AC-coupled input, a bias divider on the base, and an emitter resistor for DC stability; the 2N3904TA's well-characterized SPICE Gummel-Poon model lets designers simulate distortion before prototyping. Power dissipation rarely exceeds 50 mW in audio roles, so the 625 mW TO-92 rating provides ample thermal margin even on minimalist single-sided boards. Compared with audio-specific parts, the 2N3904TA's main compromise is its higher noise figure than low-noise transistors like the BC549C.
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Low-side Relay / Solenoid Driver Switch
Saturated switching is the second classic use for the 2N3904TA, where its 200 mA collector rating comfortably drives small relays, 12 V solenoids, and LED strings from a 3.3 V or 5 V microcontroller GPIO. Drive the base with I_B ≈ I_C/10 (forced beta 10) and the V_CE(sat) will settle near 0.2 V, keeping dissipation low. Add an inverted-logic NPN (or PNP high-side driver such as 2N3906) when the load must float; use a TVS or flyback diode when driving inductive coils. The 2N3904TA's standard E-B-C TO-92 pinout allows direct drop-in next to a logic-level MOSFET such as the 2N7000, simplifying BOM logic for designers transitioning between small BJT and small MOSFET switches.
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Logic-Level Translation (3.3 V to 5 V / 12 V)
Logic-level translation between 3.3 V microcontrollers and 5 V or 12 V peripherals is a bread-and-butter application for the 2N3904TA. Its V_CE(sat) ≤ 0.3 V and 200 mA rating mean it can pull a 5 V or 12 V rail low when activated by a 3.3 V GPIO (using a base divider or direct GPIO through a series resistor). For open-drain style translation with a pull-up on the high side, the 2N3904TA inverts logic, which is desirable when the target peripheral is active-low. With fT of 300 MHz, propagation delay stays in the tens of nanoseconds, well within I2C, SPI, and UART timing budgets. The 40 V VCEO also tolerates 24 V industrial rails when used as a 24 V to 3.3 V level shifter.
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RF / IF Amplifier Stage up to 100 MHz
With a transition frequency of 300 MHz, the 2N3904TA delivers useful gain across the AM broadcast band, the 27 MHz CB band, the 50-54 MHz amateur 6 m band, and the 88-108 MHz FM broadcast band. Designers have used it as a tuned RF amplifier, mixer, and product detector in simple superheterodyne receivers and regenerative tube replacements. For RF service, use a small emitter degeneration resistor (10-100 ohm) to stabilize gain and prevent oscillation. The 2N3904TA's relatively high hFE linearity at low collector currents makes it a decent low-noise front-end alternative to specialized RF transistors like the 2N5179, particularly in educational and experimental designs. Above 100 MHz, fT rolloff reduces usable gain to the point that a 2N3904 / 2N5179 cascade is preferable.
Empfohlen
Astable / Monostable Multivibrator Timing Circuit
The classic BJT astable multivibrator and monostable multivibrator circuits both rely on matched NPN transistors, and the 2N3904TA paired with the complementary PNP 2N3906 yields the textbook matched-transistor timing circuit. With matched hFE curves, the 2N3904TA keeps 50% duty cycle accurate without trimming, and the 300 MHz fT supports timing frequencies up to several megahertz with appropriate RC values. The TO-92 package makes through-hole breadboarding and Oscilloscope probing easy for educational settings. Designers building motor-speed controllers, PWM oscillators, and simple tone generators often start with this multivibrator topology using 2N3904TA as the NPN half of the cross-coupled pair.
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Arduino / Microcontroller General-Purpose Switching
Educators and hobbyists pairing the 2N3904TA with Arduino, Raspberry Pi Pico, or ESP32 boards treat it as the universal small-signal switch because its 200 mA rating exceeds any single GPIO output while being inexpensive and forgiving. Typical labs use it to drive LEDs that exceed the MCU's 20 mA pin limit, to switch small DC fans, and to act as a level translator between 3.3 V GPIO and 5 V peripherals. In robotic builds it serves as a relay driver for inductive loads and as a buffer between PWM outputs and MOSFET gates. The 2N3904TA's standard E-B-C pinout matches the popular SparkFun and Adafruit TO-92 breakout boards, enabling solder-on-pin-header prototyping without adapters.
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Zusammenfassung der empfohlenen Produkte
Technische Referenzdaten für 2N3904TA – Vergleich, Designhinweise und Compliance-Informationen.
Auswahlhilfe
Vergleich mit Alternativen
| Parameter | Dieses Produkt | 2N3904BU | 2N3904TAR | 2N4401TA | BC547B | P2N2222A |
|---|---|---|---|---|---|---|
| Package | TO-92-3 (Fan-Fold / TA) | TO-92-3 (Bulk pack) | TO-92-3 (Reverse tape) | TO-92-3 | TO-92-3 (EBC-L vs EBC-A pinout) | TO-92-3 |
| Brand | onsemi | onsemi | onsemi | onsemi | onsemi | onsemi |
| VCEO | 40 V | 40 V | 40 V | 40 V | 45 V | 40 V |
| Continuous Collector Current | 200 mA | 200 mA | 200 mA | 800 mA | 100 mA | 600 mA |
| Transition Frequency (fT) | 300 MHz | 300 MHz | 300 MHz | 200 MHz | 300 MHz | 300 MHz |
| DC Current Gain (hFE, typ) | 100-300 at 10 mA | 100-300 at 10 mA | 100-300 at 10 mA | 80-300 at 10 mA | 110-800 at 2 mA | 100-300 at 150 mA |
| Pinout (E/B/C viewed flat) | E-B-C | E-B-C | E-B-C | E-B-C | C-B-E (mirror) | E-B-C |
| Pb-Free / RoHS | Yes | Yes | Yes | Yes | Yes | Yes |
Wichtigste Unterscheidungsmerkmale
- Higher collector current rating than BC547 in identical package (vs. BC547B)
- Higher transition frequency than 2N4401 in same footprint (vs. 2N4401TA)
- Standard E-B-C pinout matches familiar 2N2222 heritage vs BC547's mirrored pinout (vs. BC547B)
- Pb-free / RoHS compliant by default with TA suffix (vs. Older 2N3904 stocks)
Designhinweise
Estimated: at VCE = 20 V and IC = 30 mA the dissipation is 600 mW, very close to the 625 mW 25 C rating. On a TO-92 the die cools primarily through the leads, so plan for a junction temperature rise of around (0.6 W × 200 C/W) = 120 C above ambient, putting the junction near the maximum 150 C even at room temperature. Either reduce continuous dissipation to under 250 mW or keep ambient below 50 C for reliable operation. Add generous copper pours around the three through-hole leads to drop R_thJA closer to 150 C/W in practice.
Two recurring mistakes with the 2N3904TA are (1) using it where a 2N4401 or 2N2222 is needed because the load current exceeds 200 mA, and (2) forgetting that TO-92 European equivalents such as BC547B have a reversed pinout (C-B-E vs E-B-C). Verify the part number with the board silkscreen, not by assumption, and add a series base resistor plus a reverse-biased base-emitter resistor (typically 10 kOhm) for predictable switching behavior and fast turn-off. Also avoid driving the base directly from a high-impedance source when IB > 1 mA, since hFE drops sharply at low VCE.
When laying out a TO-92 footprint, leave 2.54 mm pitch between hole centers and pad diameter 1.6 mm for the 0.55 mm typical TO-92 lead. Place the decoupling capacitor as close as possible to the collector and emitter traces; for switching circuits a 100 nF ceramic across the supply helps suppress ringing when driving inductive loads. For RF stages above 30 MHz, use a ground plane on the bottom layer and keep emitter traces short to minimize parasitic inductance that could cause oscillation. Through-hole TO-92 leads provide mechanical robustness but limit dense layout, so consider the SOT-23 MMBT3904 for compact designs.
Compliance-Informationen
Pb-Free per onsemi datasheet; not AEC-Q100 qualified (automotive grade requires MMBT3904-Q or equivalent). REACH compliance inferred from Pb-free status; confirm with onsemi compliance letter if required.
