onsemi 2N3905TF

Overview

2N3905TF from Fairchild Semiconductor is a PNP bipolar junction transistor (BJT) designed for general-purpose amplification and switching in low-power analog and digital circuits, with V_CEO = 40 V, I_C = 200 mA continuous, h_FE ≥ 30 at I_C = 0.1 mA, and TO-92 package. It serves as an active switch or small-signal amplifier in discrete logic interfaces, sensor biasing, and LED drivers.

For engineers reviewing the 2N3905TF datasheet, pinout, applications, or equivalent options, key selection criteria include its PNP polarity, 40 V V_CEO, 200 mA I_C rating, 625 mW power dissipation at 25°C, and thermal resistance of 200°C/W (junction-to-ambient), all critical for reliable operation in temperature-constrained PCB layouts.

Technical Context

The 2N3905TF operates as a silicon PNP BJT with fixed-emitter bias configuration capability and supports linear amplification up to ~100 MHz (h_fe = 2.0 at f = 100 MHz). Its DC current gain (h_FE) varies from 30 to 150 across I_C = 0.1–100 mA, and saturation voltages are specified at V_CE(sat) ≤ 0.40 V (I_C = 50 mA, I_B = 5 mA) and V_BE(sat) ≤ 0.95 V under same conditions.

Switching performance is characterized by t_d ≤ 35 ns, t_r ≤ 35 ns, t_s ≤ 200 ns, and t_f ≤ 60 ns under pulsed test conditions (≤300 µs width, ≤2% duty cycle), enabling use in moderate-speed digital logic and pulse-width modulation stages where predictable turn-on/turn-off timing is required.

Key Specifications

Pinout & Package

2N3905TF is housed in a through-hole TO-92 package with standardized three-terminal layout and JEDEC TO-92 outline dimensions (4.6 mm × 3.3 mm × 4.0 mm). Pin identification follows emitter-base-collector (E-B-C) sequence when viewing flat side with leads downward.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 2N3905TF, MPSA56 provides enhanced voltage headroom and gain stability for industrial-grade switching, while BC557 delivers broader h_FE range and marginally improved thermal behavior-both require verification of base drive network values due to differing h_FE profiles and saturation characteristics.

Availability

2N3905TF is available at Aetrix Electronics and suitable for LED driver circuits, discrete logic inverters, sensor bias networks, and level shifter interfaces requiring stable component supply and long-term obsolescence management.

Supply support for 2N3905TF 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

Fairchild Semiconductor was a US-based semiconductor company specializing in power management, analog, and discrete components before its acquisition by ON Semiconductor in 2016.

The 2N3905TF belongs to Fairchild's legacy general-purpose transistor family, engineered for broad compatibility in analog amplification, switching, and interface design across consumer, industrial, and educational electronics.

FAQ

What is the maximum collector-emitter voltage rating for the 2N3905TF?

The 2N3905TF has a maximum collector-emitter voltage (V_CEO) rating of 40 V at T_A = 25°C. This value is defined under open-base conditions and must not be exceeded to prevent avalanche breakdown. Derating is not specified beyond ambient temperature limits, and operation above 40 V risks permanent device failure. The 2N3905TF datasheet confirms this rating applies to the TO-92 packaged variant.

Does the 2N3905TF support switching applications, and what are its key timing parameters?

Yes, the 2N3905TF is qualified for switching use with documented delay time (t_d) ≤ 35 ns, rise time (t_r) ≤ 35 ns, storage time (t_s) ≤ 200 ns, and fall time (t_f) ≤ 60 ns under pulsed test conditions (≤300 µs width, ≤2% duty cycle). These values assume V_CC = 3.0 V and I_CS = 10 mA. The 2N3905TF's PNP architecture makes it especially effective in high-side switch configurations where fast turn-off is critical.

What is the DC current gain (h_FE) range of the 2N3905TF across operating conditions?

The 2N3905TF exhibits h_FE = 30 (min) at I_C = 0.1 mA, rising to 150 (max) at I_C = 10 mA, then decreasing to 15 at I_C = 100 mA-all measured at V_CE = 1.0 V and T_A = 25°C. This nonlinear gain profile means the 2N3905TF performs best in low-to-moderate current amplification roles. Designers must verify bias point stability across temperature, as the 2N3905TF's h_FE shifts with junction temperature.

Is the 2N3905TF RoHS compliant, and what is its lead-free status?

The 2N3905TF was originally manufactured prior to mandatory RoHS enforcement and is not inherently RoHS-compliant in its legacy form. However, Fairchild's Rev G datasheet does not declare lead-free status, and no Pb-free variant (e.g., 2N3905TF-LEADFREE) is referenced in official documentation. For new designs requiring RoHS compliance, engineers should consider modern alternatives such as the NSS60201MR6T1G (SOT-23, PNP, RoHS-compliant) or verify current manufacturing status directly with ON Semiconductor.

What thermal derating applies to the 2N3905TF above 25°C ambient temperature?

The 2N3905TF specifies a linear thermal derating factor of 5.0 mW/°C above 25°C ambient, applied to its 625 mW maximum power dissipation rating. This means usable power drops to 500 mW at 50°C ambient and 375 mW at 75°C. The derating is based on R_θJA = 200°C/W and assumes standard TO-92 mounting on FR-4 PCB with no heatsink. The 2N3905TF's maximum junction temperature remains 150°C across its full operating range.