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

onsemi 2N3905

Name: 2N3905
Brand: onsemi
SKU: 2N3905
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 2N3905

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: 2N3905.pdf

Description:: TRANS PNP 40V 0.2A TO-92

Quantity:: RFQ Add To RFQ list

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Product details

Overview

2N3905 from ON Semiconductor is a PNP bipolar junction transistor designed for general-purpose amplification and switching in low-power analog and digital circuits, with confirmed V_CEO = 40 V, I_C = 200 mA continuous, h_FE = 30–150 (at I_C = 0.1–100 mA), V_CE(sat) = 0.25 V (I_C = 10 mA, I_B = 1 mA), and TO-92 package. It is commonly used in discrete logic inverters, level shifters, and small-signal amplifier stages.

For engineers reviewing the 2N3905 datasheet, pinout, applications, or equivalent options, key selection considerations include its PNP polarity, DC current gain variation across collector current range, thermal derating above 25°C, saturation voltage behavior at varying drive conditions, and compatibility with legacy through-hole prototyping and low-voltage bias networks.

Technical Context

The 2N3905 operates as a standard silicon PNP BJT with fixed-emitter biasing topology, supporting both linear amplification (V_CE ≥ 1 V) and saturated switching (V_CE ≤ 0.4 V). Its h_FE exhibits strong collector-current dependence-ranging from 30 at 100 mA to 150 at 0.1 mA-and its small-signal h_fe reaches 200 at 1 mA and 10 V_CE.

Thermal performance is defined by R_θJA = 200 °C/W and R_θJC = 83.3 °C/W, with maximum junction temperature limited to +150°C. Switching is characterized by t_d = 35 ns, t_r = 35 ns, t_s = 200 ns, and t_f = 60 ns under specified pulsed test conditions (≤300 µs, ≤2% duty cycle).

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	40 V - Maximum safe collector-emitter voltage before breakdown; sets upper rail limit for common-emitter switch or amplifier stage.
I_C (continuous)	200 mA - Absolute max DC collector current; usable up to 100 mA for reliable general-purpose operation per design intent.
h_FE range	30–150 - DC current gain varies significantly with operating point; requires bias network validation across expected I_C range.
V_CE(sat)	0.25 V @ I_C=10 mA/I_B=1 mA - Confirmed low saturation voltage enables efficient low-side PNP switching in 5 V logic interfaces.
P_D (25°C)	625 mW - Total power dissipation limit; derates linearly at 5.0 mW/°C above 25°C ambient.
f_T	Not specified - No transition frequency value provided in official documentation; not rated for RF or high-speed switching >10 MHz.

Pinout & Package

2N3905 is housed in a TO-92 plastic package with standardized lead orientation: flat side facing viewer, leads downward, left-to-right pin order is Emitter (E), Base (B), Collector (C).

Pin/Terminal	Circuit Role	Design Meaning
E (Emitter)	Current source terminal for PNP device	Connected to higher potential rail in common-emitter configuration; base current flows out of this terminal.
B (Base)	Control electrode for minority-carrier injection	Receives reverse-biased current to turn on; requires external current-limiting resistor in most switch applications.
C (Collector)	Current sink terminal	Typically tied to load and ground-return path; voltage swing capability limited by V_CEO = 40 V rating.

Key Features

Feature	Design Value
PNP polarity with complementary 2N3904 pairing	Enables direct implementation of push-pull, differential pair, and phase-splitter topologies without level-shifting circuitry.
Low V_CE(sat) at moderate currents	0.25 V saturation ensures <1% voltage drop across transistor in 5 V logic-level switches, minimizing power loss and heat rise.
Wide operating temperature range	−55°C to +150°C junction range supports deployment in industrial control, automotive under-hood auxiliary circuits, and outdoor sensor nodes.
Established reliability and second-source availability	Manufactured by ON Semiconductor with documented qualification per JESD22-A108; widely available from multiple authorized distributors with full traceability.

Applications

Discrete Logic Inverter	Low-Voltage Level Shifter
Use Scenario: Converting TTL/CMOS logic-high (3.3 V or 5 V) to active-low output in microcontroller GPIO expansion. IC Role / Device Role / Timing Role: PNP switch configured in common-emitter mode, driven by MCU output pin through base resistor. Use Value: Delivers clean inversion with <0.25 V output low and rail-to-rail high swing; avoids need for dedicated logic gate IC.	Use Scenario: Translating 1.8 V I²C bus signals to 3.3 V domain while maintaining open-drain compatibility. IC Role / Device Role / Timing Role: PNP-based passive pull-up translator with emitter tied to 3.3 V, base driven by 1.8 V signal via resistor. Use Value: Enables bidirectional voltage translation without timing skew or active buffering; supports standard I²C rise/fall time specs.
Analog Signal Amplifier	LED Driver Switch
Use Scenario: Boosting weak sensor outputs (e.g., thermistor divider, photodiode transimpedance stage) in battery-powered instrumentation. IC Role / Device Role / Timing Role: Common-emitter amplifier with emitter degeneration resistor and collector load; biased for Class-A operation. Use Value: Provides stable 30–100× voltage gain at sub-100 kHz bandwidth; noise figure of 5.0 dB at 100 µA improves SNR in low-level analog front ends.	Use Scenario: Driving indicator LEDs in industrial HMI panels where microcontroller GPIO cannot sink sufficient current. IC Role / Device Role / Timing Role: Saturated PNP switch with collector connected to LED anode and cathode grounded through current-limiting resistor. Use Value: Supports up to 100 mA LED current with <0.4 V dropout, enabling bright illumination from 3.3 V or 5 V rails without thermal throttling.

Discrete Logic Inverter

Low-Voltage Level Shifter

Use Scenario: Converting TTL/CMOS logic-high (3.3 V or 5 V) to active-low output in microcontroller GPIO expansion.

IC Role / Device Role / Timing Role: PNP switch configured in common-emitter mode, driven by MCU output pin through base resistor.

Use Value: Delivers clean inversion with <0.25 V output low and rail-to-rail high swing; avoids need for dedicated logic gate IC.

Use Scenario: Translating 1.8 V I²C bus signals to 3.3 V domain while maintaining open-drain compatibility.

IC Role / Device Role / Timing Role: PNP-based passive pull-up translator with emitter tied to 3.3 V, base driven by 1.8 V signal via resistor.

Use Value: Enables bidirectional voltage translation without timing skew or active buffering; supports standard I²C rise/fall time specs.

Analog Signal Amplifier

LED Driver Switch

Use Scenario: Boosting weak sensor outputs (e.g., thermistor divider, photodiode transimpedance stage) in battery-powered instrumentation.

IC Role / Device Role / Timing Role: Common-emitter amplifier with emitter degeneration resistor and collector load; biased for Class-A operation.

Use Value: Provides stable 30–100× voltage gain at sub-100 kHz bandwidth; noise figure of 5.0 dB at 100 µA improves SNR in low-level analog front ends.

Use Scenario: Driving indicator LEDs in industrial HMI panels where microcontroller GPIO cannot sink sufficient current.

IC Role / Device Role / Timing Role: Saturated PNP switch with collector connected to LED anode and cathode grounded through current-limiting resistor.

Use Value: Supports up to 100 mA LED current with <0.4 V dropout, enabling bright illumination from 3.3 V or 5 V rails without thermal throttling.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BC557	V_CEO = 45 V, h_FE = 110–800 (at I_C = 2 mA), SOT-23 package	Higher gain consistency at low currents; surface-mount only; lacks TO-92 mechanical compatibility	Select BC557 when board space is constrained and high h_FE at µA–mA bias is required; verify PCB footprint and thermal relief.
MPSA92	V_CEO = 300 V, I_C = 500 mA, TO-92 package, h_FE = 25–100	Higher voltage/current ratings but lower gain uniformity; intended for HV switching, not general-purpose analog	Choose MPSA92 only for applications requiring >60 V blocking or >150 mA continuous current; avoid for precision gain-critical stages.

Compared with BC557 and MPSA92, the 2N3905 offers optimal balance of through-hole manufacturability, predictable mid-range h_FE, and proven stability in legacy designs-making it preferred for prototyping, education, and cost-sensitive consumer electronics where 40 V/200 mA limits are sufficient.

Availability

2N3905 is available at Aetrix Electronics and suitable for discrete logic inverters, low-voltage level shifters, and LED driver switches requiring stable component supply, long-term obsolescence management, and consistent parametric performance across production lots.

Supply support for 2N3905 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, sensors, and logic devices for automotive, industrial, and cloud infrastructure markets.

The 2N3905 belongs to ON Semiconductor's legacy general-purpose transistor product line, originally developed for broad adoption in educational labs, prototyping, and cost-sensitive consumer electronics where reliability, second-source availability, and through-hole assembly compatibility are prioritized.

FAQ

What is the maximum collector-emitter voltage rating for the 2N3905?

The 2N3905 has a maximum collector-emitter voltage (V_CEO) rating of 40 V at T_A = 25°C. This rating applies under DC or pulsed conditions with duty cycle ≤2% and pulse width ≤300 µs. Exceeding 40 V risks avalanche breakdown and permanent device failure. Derating is not specified beyond the absolute maximum limit, so operation near 40 V requires careful margin analysis and thermal verification.

Is the 2N3905 pin-compatible with the 2N3904?

No, the 2N3905 is not pin-compatible with the 2N3904 in functional circuits despite sharing the same TO-92 package and pin order (E-B-C). The 2N3904 is NPN while the 2N3905 is PNP, so swapping them without reversing biasing and load connections will prevent circuit operation. Their complementary nature means they are used in paired configurations-not as drop-in replacements.

What is the typical noise figure of the 2N3905 and under what conditions is it measured?

The 2N3905 has a noise figure (NF) of 5.0 dB, measured at V_CE = 5.0 V, I_C = 100 µA, R_S = 1.0 kΩ, and bandwidth from 10 Hz to 15.7 kHz. This value reflects low-frequency audio and sensor signal conditioning performance. NF increases at higher currents and frequencies; no data is provided above 15.7 kHz, confirming the device is not optimized for RF or wideband applications.

Does the 2N3905 have a specified transition frequency (f_T)?

No, the official ON Semiconductor datasheet for the 2N3905 does not specify transition frequency (f_T). Small-signal current gain (h_fe) is provided at 100 MHz (2.0) and 1 kHz (50–200), but no f_T value is listed or derivable from published curves. Therefore, the 2N3905 should not be selected for applications requiring known RF gain-bandwidth performance or high-speed switching above ~10 MHz.

Can the 2N3905 be used in surface-mount designs?

The standard 2N3905 is only offered in the through-hole TO-92 package. While functionally equivalent SMT alternatives exist (e.g., BC557, SMMBT3905), the 2N3905 itself has no official SMT variant. Attempting to mount TO-92 devices on SMT pads violates IPC standards, compromises thermal and mechanical reliability, and voids manufacturer warranty. Use verified SMT equivalents instead.

2N3905 Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

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

Packaging:: Bulk

Product Status:: Active

Transistor Type:: PNP

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

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

Vce Saturation (Max) @ Ib, Ic:: 400mV @ 5mA, 50mA

Current - Collector Cutoff (Max):: 50nA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 50 @ 10mA, 1V

Power - Max:: 625 mW

Frequency - Transition:: 200MHz

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

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92

2N3905 FAQ

1.How can I place an order for 2N3905 through Aetrix?

Please submit a Request for Quotation (RFQ) for 2N3905 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 2N3905 reliable?

The price and inventory of 2N3905 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 2N3905 is usually 5 days.

3.What payment methods are accepted for 2N3905?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 2N3905 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 2N3905?

2N3905 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 2N3905 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 2N3905?

For technical support, including 2N3905 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 2N3905 requirements.

6.How does Aetrix verify that 2N3905 is sourced from the original manufacturer or authorized distributors?

All 2N3905 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 2N3905 meets industry standards.

7.What is the process for return or replacement of 2N3905?

All 2N3905 units undergo pre-shipment inspection (PSI). If there is an issue with 2N3905, 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 2N3905 part is unused and in its original packaging.

Return procedure for 2N3905:

1.Submit a request within 90 days.

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

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