MMBT3904 - 40V NPN Small-Signal Transistor, 200mA | Multi-Source
MPN: MMBT3904 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.13 | $0.13 |
| 10 | $0.11 | $1.10 |
| 100 | $0.08 | $8.00 |
| 500 | $0.06 | $30.00 |
| 1,000 | $0.05 | $50.00 |
| 3,000 | $0.04 | $120.00 |
MMBT3904 Overview
A small-signal BJT is a type of bipolar transistor optimized for low-current amplification and switching rather than power delivery. In the semiconductor taxonomy, the MMBT3904 sits under: BJT -> bipolar transistor -> discrete semiconductor. It functions as the NPN complement to the MMBT3906 (PNP) and is the surface-mount counterpart to the through-hole 2N3904, sharing the same die-level electrical targets but in a smaller SOT-23 footprint.
Key features include a 40 V collector-emitter breakdown (VCEO), 60 V collector-base breakdown (VCBO), a DC current gain (hFE) range of 100 to 300 at 10 mA, and a power dissipation of approximately 200 to 350 mW depending on board layout. The epitaxial planar die construction provides tight parametric distribution and the complementary MMBT3906 PNP enables push-pull output stages. Most datasheet revisions are lead-free, fully RoHS compliant, and several are AEC-Q101 qualified for automotive use.
Architecturally, the device is designed as a general-purpose amplifier and switch, with a useful dynamic range extending to 100 mA as a switch and 100 MHz as an amplifier. The SOT-23 package occupies roughly 6 mm² of board area and is the de-facto industry standard for low-power SMD transistors.
Typical applications include general-purpose switching circuits, signal amplification, interface logic level shifting, oscillator building blocks, driver stages for LEDs and small relays, and complementary push-pull pairs in audio output stages. Designers should select it whenever a low-cost, widely second-sourced NPN transistor is needed for non-critical analog or digital switching tasks.
When designing with the MMBT3904, observe the maximum collector dissipation (typically 200 mW on a minimal pad, up to 350 mW with the JEDEC 1 oz copper test board of 15 mm x 15 mm). For switching applications, include a base drive resistor to control saturation and improve turn-off time.
Drop-in alternatives for MMBT3904 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with MMBT3904 (same form factor and footprint) — differing in Package, Transition Frequency (fT), DC Current Gain (hFE), RoHS Status, Operating Temperature Range.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
MMBT3904LT1G
✅ Drop-In📋 Reference alternative (not in catalog)
MMBT3904LT3G
✅ Drop-In📋 Reference alternative (not in catalog)
SMMBT3904
✅ Drop-In📋 Reference alternative (not in catalog)
MMBT3904,215
✅ Drop-In✓ In Stock
$0.015 / Unit
View Datasheet →MMBT3904-13P
✅ Drop-In📋 Reference alternative (not in catalog)
MMBT3904-TP
✅ Drop-In📋 Reference alternative (not in catalog)
MMBT3904 Maximum Ratings & Electrical Characteristics
| Transistor Type | NPN |
| Package | SOT-23 (TO-236AB), 3 pins |
| Collector-Emitter Voltage (Vceo) | 40 V |
| Collector-Base Voltage (Vcbo) | 60 V |
| Emitter-Base Voltage (Vebo) | 6 V |
| Continuous Collector Current (IC) | 200 mA |
| Power Dissipation (PD) | 200 mW to 350 mW (board-dependent) |
| Transition Frequency (ft) | 300 MHz (typ, at VCE=20 V, IC=10 mA) |
| DC Current Gain (hFE) | 100 to 300 (at IC=10 mA, VCE=1.0 V) |
| Noise Figure | 5 dB (max) |
| Operating Temperature Range | -55C to +150C (junction) |
| Mounting Type | Surface Mount |
| Complementary PNP Part | MMBT3906 |
| Lead-Free / RoHS | Yes (fully RoHS compliant per datasheet) |
| Automotive Grade (AEC-Q101) | Qualified by selected suppliers |
MMBT3904 Pin Configuration
| Pin 1 | BASE — Base control terminal |
| Pin 2 | EMITTER — Emitter terminal (grounded in common-emitter configurations) |
| Pin 3 | COLLECTOR — Collector terminal (load connection) |
Typical Applications
MMBT3904 is suitable for 6 applications: General-Purpose Switching Circuit, Signal Amplification Stage, Logic Level Shifter, Oscillator and Timer Building Block, LED Driver and Indicator Stage, Complementary Push-Pull Audio Output.
General-Purpose Switching Circuit
The MMBT3904's 40V VCEO, 200mA IC, and 300MHz fT make it ideal for general-purpose low-side switching applications such as driving LEDs, small relays, and logic-level shifters. Its 100-300 hFE range at 10mA provides ample base drive margin when interfaced from 3.3V or 5V microcontrollers via a series base resistor. The SOT-23 footprint enables dense PCB layouts in consumer electronics and IoT devices, while the multi-vendor second-source availability ensures supply chain resilience.
Recommended
Signal Amplification Stage
With a 300 MHz transition frequency and an hFE of 100 to 300 at 10 mA, the MMBT3904 functions well as a small-signal amplifier in the audio to RF range below 100 MHz. It is commonly deployed in pre-amplifier stages, IF buffers, and general-purpose analog gain blocks where cost per channel matters more than ultra-low noise. The complementary MMBT3906 enables matched differential or push-pull amplifier topologies for balanced signal paths.
Recommended
Logic Level Shifter
The MMBT3904 is widely used as a single-transistor level shifter between 3.3V microcontrollers and 5V or 12V peripherals, leveraging its 40V VCEO to tolerate higher rail voltages. With a base resistor sized for the source logic high level and a pull-up on the collector, the circuit achieves fast edges suitable for GPIO, I2C, or UART bridging. The 200mA collector rating comfortably drives opto-couplers, small SSR coils, and indicator LEDs in interface cards.
Recommended
Oscillator and Timer Building Block
The MMBT3904's 300MHz fT and predictable hFE characteristics make it a reliable active device for astable and monostable multivibrator circuits, RC oscillators, and 555-style timer replacements. Its fast switching response supports stable oscillation from sub-audio to several MHz, and the SOT-23 package keeps oscillator sections compact in hobby and educational designs. Designers should add base resistor bias networks to stabilize amplitude against temperature variation.
Recommended
LED Driver and Indicator Stage
The MMBT3904 efficiently drives indicator LEDs, optocouplers, and small seven-segment displays from logic-level inputs. At 200mA continuous collector current, it can sink or source a chain of indicator LEDs with proper base bias, and its 40V rating tolerates higher supply rails used in industrial HMI panels. The SOT-23 SMD package suits automated pick-and-place assembly for volume production of consumer and industrial control boards.
Recommended
Complementary Push-Pull Audio Output
Paired with the MMBT3906 PNP, the MMBT3904 forms a Class-B push-pull output stage capable of delivering modest audio power into headphones or small speakers. The matched VCEO and hFE characteristics ensure symmetrical clipping and low crossover distortion in low-power audio buffer designs. Although not a high-fidelity audio transistor, it suffices for intercom, toy, and hobby audio applications where cost is critical.
Recommended
Recommended Products Summary
Engineering reference data for MMBT3904 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | MMBT3904LT1G | MMBT3904LT3G | SMMBT3904 | MMBT3904,215 | MMBT3904-13P | MMBT3904-TP |
|---|---|---|---|---|---|---|---|
| Brand | onsemi | onsemi | onsemi | onsemi | Nexperia | Diodes Incorporated | Micro Commercial Components |
| Package | SOT-23 | SOT-23 - same | SOT-23 - same | SOT-23 - same | SOT-23 (TO-236AB) - same | SOT-23 - same | SOT-23 - same |
| Transistor Type | NPN | NPN | NPN | NPN | NPN | NPN | NPN |
| VCEO (V) | 40 V | 40 V | 40 V | 40 V | 40 V | 40 V | 40 V |
| VCBO (V) | 60 V | 60 V | 60 V | 60 V | 60 V | 60 V | 60 V |
| Continuous IC (mA) | 200 mA | 200 mA | 200 mA | 200 mA | 200 mA | 200 mA | 200 mA |
| Power Dissipation (mW) | 200-350 mW | 200-350 mW | 200-350 mW | 200-350 mW | 250 mW | 200-350 mW | 200-350 mW |
| Transition Frequency fT (MHz) | 300 MHz | 300 MHz | 300 MHz | 300 MHz | 300 MHz | 300 MHz | 300 MHz |
| hFE Range (at 10 mA) | 100 to 300 | 100 to 300 | 100 to 300 | 100 to 300 | 100 to 300 | 100 to 300 | 100 to 300 |
| RoHS / Lead-Free | Yes | Yes | Yes (Halogen/BFR-free) | Yes | Yes | Yes | Yes |
Key Differentiators
- Wider VCBO headroom than the BC847B (vs BC847B)
- Higher continuous collector current than the BC847B (vs BC847B)
- Multi-vendor second-source availability (vs Vendor-locked equivalents)
Design Notes
Estimated: on a JEDEC-standard 15 mm x 15 mm 1 oz copper test pad, the MMBT3904 dissipates up to 350 mW; on a minimal SOT-23 land pattern, this drops to approximately 200 mW. For continuous 200 mA loads at elevated ambient temperature, ensure PCB copper area supports the thermal path or use multiple transistors in parallel. Refer to JESD22-A114 and JESD22-A115 thermal test methods per the manufacturer datasheet.
Do not exceed VCEO = 40 V, VCBO = 60 V, or VEBO = 6 V. For inductive loads such as relays or small solenoids, place a flyback diode across the coil to protect the collector from kickback voltage. When driving the base directly from a 3.3 V or 5 V microcontroller GPIO, always include a series base resistor to limit base current and avoid saturation-induced storage time delays in switching applications.
Use a SOT-23 land pattern per IPC-7351 with thermal pad copper tied to the collector pin (pin 3). For switching applications above 50 mA or frequencies above 10 MHz, keep the base trace short and place the base resistor within 5 mm of the base pin. Star-ground the emitter return to minimize common-emitter gain variations in amplifier topologies.
Compliance Information
Fully RoHS compliant and lead-free per manufacturer datasheets. Selected supplier versions are AEC-Q101 qualified for automotive; consult individual vendor datasheets. Halogen-free/BFR-free per the onsemi MMBT3904LT3G datasheet. Thermal test methods referenced per JEDEC JESD22-A114 and JESD22-A115.
