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Home > Products > Discrete Semiconductor Products > Transistors > Bipolar (BJT) > Single Bipolar Transistors

onsemi 2N3904_D28Z

Name: 2N3904_D28Z
Brand: onsemi
SKU: 2N3904_D28Z
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 2N3904_D28Z

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-226-3, TO-92-3 (TO-226AA) Formed Leads

Datasheet:: 2N3904_D28Z.pdf

Description:: TRANS NPN 40V 0.2A TO-92-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

2N3904_D28Z from ON Semiconductor is a silicon NPN general-purpose bipolar junction transistor used for low-power amplification and switching in discrete analog and digital circuits. It delivers DC current gain (h_FE) of 70–300 at I_C = 1.0 mA, V_CE = 1.0 V; supports 100 MHz current-gain bandwidth (f_T); and operates with V_CEO = 40 V, I_C = 200 mA continuous, in TO-92 package - commonly deployed in signal conditioning stages of sensor interfaces and low-voltage logic-level translation.

For engineers reviewing the 2N3904_D28Z datasheet, pinout, applications, or equivalent options, this page provides verified electrical parameters, thermal derating data, switching timing values (t_d, t_r, t_s, t_f), noise figure (5.0 dB), and real-world design context for amplifier biasing, active load switching, and pulse generation circuits.

Technical Context

The 2N3904_D28Z implements a planar epitaxial NPN structure optimized for high-speed small-signal operation. Its f_T = 300 MHz and low output capacitance (C_obo = 4.0 pF) support stable RF amplification up to VHF bands when properly biased. The device exhibits predictable h_FE variation across collector current (10 mA to 100 mA), enabling reliable Class-A amplifier design with minimal thermal drift.

Switching behavior is characterized by t_s = 200 ns (storage time) and t_f = 50 ns (fall time) under standardized test conditions (V_CC = 3.0 V, I_C = 10 mA, I_B1 = I_B2 = 1.0 mA), making it suitable for medium-speed digital logic interfacing and PWM-driven LED/relay control where turn-off speed matters.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	40 V - Maximum safe collector-emitter voltage before breakdown; sets upper limit for supply rail in common-emitter switch designs.
I_C (continuous)	200 mA - Absolute max DC collector current; usable up to 100 mA for sustained linear amplification without thermal runaway.
h_FE @ I_C=1 mA	70–300 - DC current gain range defining base drive requirements for low-current switching or preamplifier stages.
f_T	300 MHz - Unity-gain frequency confirming suitability for audio and low-VHF amplification (e.g., IF stages up to 30 MHz).
NF @ 100 μA	5.0 dB - Measured noise figure at 10 Hz–15.7 kHz with R_S = 1 kΩ; enables low-noise microphone preamp use with <10 nV/√Hz input noise density.
t_s / t_f	200 ns / 50 ns - Storage and fall times measured under pulsed conditions; informs minimum achievable PWM frequency in saturated-switch applications.
P_D @ 25°C	625 mW - Total power dissipation in TO-92 package; requires ≥5.0 mW/°C derating above ambient for thermal stability.

Pinout & Package

2N3904_D28Z is housed in a through-hole TO-92 3-lead package with standard EBC (Emitter-Base-Collector) pin configuration viewed from flat side with leads down. Package outline complies with JEDEC TO-92 variant AA; lead spacing is 0.5 inch (12.7 mm) between outer pins, with center-to-center pitch of 0.25 inch (6.35 mm).

Pin/Terminal	Circuit Role	Design Meaning
E (Emitter)	Current sink terminal in NPN operation	Connected to ground or low-impedance return path; determines emitter-follower output impedance and bias stability.
B (Base)	Control electrode for carrier injection	Receives current-limited drive (typically via 1–10 kΩ resistor); base-emitter voltage drop (V_BE(sat) = 0.65–0.95 V) defines forward-bias threshold.
C (Collector)	Current source terminal in NPN operation	Connected to load and positive supply; collector-emitter saturation voltage (V_CE(sat) ≤ 0.3 V @ I_C=50 mA) minimizes conduction loss in switch mode.

Key Features

Feature	Design Value
High f_T with low C_obo	300 MHz gain-bandwidth product and 4.0 pF output capacitance enable stable small-signal amplification up to 30 MHz without peaking.
Wide h_FE range across I_C	h_FE = 40–300 across I_C = 0.1–100 mA allows flexible bias point selection for Class-A, -AB, or saturated switching without gain collapse.
Low noise at audio frequencies	5.0 dB noise figure at 100 μA collector current supports high-SNR preamplifier stages in electret microphone and sensor signal chains.
Controlled saturation characteristics	V_CE(sat) ≤ 0.3 V and V_BE(sat) ≤ 0.95 V at I_C/I_B = 10 ensure predictable on-state voltage drop and minimal power loss in digital interface applications.
Robust thermal rating	Junction temperature range of –55°C to +150°C and 625 mW dissipation allow operation in industrial environments with passive heatsinking only.

Applications

Audio Preamplifier Stage	Microcontroller GPIO Level Shifter
Use Scenario: Amplifying weak signals from electret microphones or piezoelectric sensors into ADC-input range. IC Role / Device Role / Timing Role: Discrete NPN transconductance amplifier in common-emitter configuration with emitter degeneration. Use Value: 5.0 dB noise figure and 300 MHz f_T preserve signal integrity across 20 Hz–20 kHz while supporting gain >100 without oscillation.	Use Scenario: Converting 3.3 V logic outputs from microcontrollers to drive 5 V TTL-compatible inputs or LEDs. IC Role / Device Role / Timing Role: Saturated NPN switch translating logic levels with fast turn-on/off transitions. Use Value: t_d/t_r = 35 ns each and t_f = 50 ns enable clean 10 MHz digital waveform edges without overshoot or ringing.
Linear Voltage Regulator Pass Element	Low-Frequency Pulse Generator
Use Scenario: Acting as series pass transistor in adjustable linear regulators (e.g., LM317-based circuits) delivering ≤100 mA load current. IC Role / Device Role / Timing Role: Linear-mode current amplifier controlling output voltage via base bias network. Use Value: h_FE ≥ 70 at I_C = 100 mA ensures stable regulation with <1% line/load regulation error under varying thermal conditions.	Use Scenario: Generating square-wave clock or timing pulses in astable multivibrator circuits for system reset or watchdog timing. IC Role / Device Role / Timing Role: Cross-coupled NPN switch in emitter-coupled oscillator topology. Use Value: Predictable t_s = 200 ns and consistent V_BE(sat) enable repeatable 1–500 kHz oscillation frequencies with ±5% tolerance across temperature.

Audio Preamplifier Stage

Microcontroller GPIO Level Shifter

Use Scenario: Amplifying weak signals from electret microphones or piezoelectric sensors into ADC-input range.

IC Role / Device Role / Timing Role: Discrete NPN transconductance amplifier in common-emitter configuration with emitter degeneration.

Use Value: 5.0 dB noise figure and 300 MHz f_T preserve signal integrity across 20 Hz–20 kHz while supporting gain >100 without oscillation.

Use Scenario: Converting 3.3 V logic outputs from microcontrollers to drive 5 V TTL-compatible inputs or LEDs.

IC Role / Device Role / Timing Role: Saturated NPN switch translating logic levels with fast turn-on/off transitions.

Use Value: t_d/t_r = 35 ns each and t_f = 50 ns enable clean 10 MHz digital waveform edges without overshoot or ringing.

Linear Voltage Regulator Pass Element

Low-Frequency Pulse Generator

Use Scenario: Acting as series pass transistor in adjustable linear regulators (e.g., LM317-based circuits) delivering ≤100 mA load current.

IC Role / Device Role / Timing Role: Linear-mode current amplifier controlling output voltage via base bias network.

Use Value: h_FE ≥ 70 at I_C = 100 mA ensures stable regulation with <1% line/load regulation error under varying thermal conditions.

Use Scenario: Generating square-wave clock or timing pulses in astable multivibrator circuits for system reset or watchdog timing.

IC Role / Device Role / Timing Role: Cross-coupled NPN switch in emitter-coupled oscillator topology.

Use Value: Predictable t_s = 200 ns and consistent V_BE(sat) enable repeatable 1–500 kHz oscillation frequencies with ±5% tolerance across temperature.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN general-purpose amplifier applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
MMBT3904	SOT-23 surface-mount package; lower P_D = 350 mW; identical electrical specs except R_θJA = 357°C/W vs. 200°C/W for TO-92.	Preferred for space-constrained PCBs; unsuitable for >150 mA continuous loads due to thermal limits.	Select MMBT3904 when board area is critical and peak power dissipation remains below 250 mW.
BC547B	V_CEO = 45 V; h_FE = 200–450 @ I_C = 2 mA; f_T ≈ 300 MHz; TO-92 package but different pinout (E-C-B).	Higher gain and breakdown voltage support higher-voltage analog stages; pinout mismatch requires layout revision.	Choose BC547B only if higher V_CEO or tighter h_FE binning is required and PCB redesign is acceptable.

Compared with MMBT3904 and BC547B, the 2N3904_D28Z offers optimal thermal performance in through-hole designs, standardized EBC pinout for legacy compatibility, and proven stability in audio-frequency amplifiers - making it the preferred choice for prototyping, repair, and industrial control boards where reliability and serviceability matter.

Availability

2N3904_D28Z is available at Aetrix Electronics and suitable for audio preamplifier stages, microcontroller GPIO level shifting, and linear voltage regulator pass elements requiring stable component supply, long-term obsolescence management, and full traceability.

Supply support for 2N3904_D28Z includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

ON Semiconductor is a global semiconductor manufacturer specializing in energy-efficient power management, analog, and discrete devices for automotive, industrial, and consumer applications.

The 2N3904_D28Z belongs to ON Semiconductor's legacy general-purpose transistor family, originally developed by Fairchild and maintained for broad compatibility in analog signal conditioning, switching, and educational circuits.

FAQ

What is the maximum collector-emitter voltage rating for 2N3904_D28Z?

The 2N3904_D28Z has a guaranteed V_CEO rating of 40 V at T_A = 25°C. This is the maximum voltage that can be applied between collector and emitter with the base open before breakdown occurs. Operation above this value risks permanent damage, and derating is recommended for elevated temperatures or reliability-critical applications.

Does 2N3904_D28Z support audio-frequency amplification?

Yes, the 2N3904_D28Z supports audio-frequency amplification with a noise figure of 5.0 dB at 100 μA collector current and 10 Hz–15.7 kHz bandwidth. Its f_T = 300 MHz and stable h_FE across 0.1–100 mA make it suitable for high-fidelity preamplifier stages, especially when configured with emitter degeneration for linearity.

What is the pin configuration of 2N3904_D28Z in TO-92 package?

The 2N3904_D28Z uses standard EBC (Emitter-Base-Collector) pinout in TO-92: with the flat side facing you and leads pointing downward, left-to-right pins are Emitter, Base, Collector. This matches JEDEC TO-92 variant AA and ensures compatibility with existing sockets and schematics designed for legacy 2N3904 variants.

Can 2N3904_D28Z be used as a saturated switch?

Yes, the 2N3904_D28Z is routinely used as a saturated switch with V_CE(sat) ≤ 0.3 V at I_C = 50 mA and I_B = 5.0 mA. Its t_s = 200 ns and t_f = 50 ns support reliable switching up to ~500 kHz in low-power digital interfaces, provided base drive is adequately sized to avoid slow turn-off.

How does thermal performance of 2N3904_D28Z compare to SOT-23 versions?

The 2N3904_D28Z in TO-92 offers superior thermal performance versus SOT-23-packaged equivalents: its R_θJA = 200°C/W and P_D = 625 mW allow higher continuous current handling without heatsinking. In contrast, MMBT3904 (SOT-23) has R_θJA = 357°C/W and P_D = 350 mW, limiting its use to lower-power or pulsed applications.

2N3904_D28Z Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-226-3, TO-92-3 (TO-226AA) Formed Leads

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 200 mA

Voltage - Collector Emitter Breakdown (Max):: 40 V

Vce Saturation (Max) @ Ib, Ic:: 300mV @ 5mA, 50mA

Current - Collector Cutoff (Max):: -

DC Current Gain (hFE) (Min) @ Ic, Vce:: 100 @ 10mA, 1V

Power - Max:: 625 mW

Frequency - Transition:: 300MHz

Operating Temperature:: -55°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92-3

2N3904_D28Z FAQ

1.How can I place an order for 2N3904_D28Z through Aetrix?

Please submit a Request for Quotation (RFQ) for 2N3904_D28Z on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for 2N3904_D28Z reliable?

The price and inventory of 2N3904_D28Z are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 2N3904_D28Z is usually 5 days.

3.What payment methods are accepted for 2N3904_D28Z?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 2N3904_D28Z transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 2N3904_D28Z?

2N3904_D28Z orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 2N3904_D28Z order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for 2N3904_D28Z?

For technical support, including 2N3904_D28Z datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 2N3904_D28Z requirements.

6.How does Aetrix verify that 2N3904_D28Z is sourced from the original manufacturer or authorized distributors?

All 2N3904_D28Z products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that 2N3904_D28Z meets industry standards.

7.What is the process for return or replacement of 2N3904_D28Z?

All 2N3904_D28Z units undergo pre-shipment inspection (PSI). If there is an issue with 2N3904_D28Z, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The 2N3904_D28Z part is unused and in its original packaging.

Return procedure for 2N3904_D28Z:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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