onsemi 2N3905TAR

Overview

2N3905TAR from Fairchild Semiconductor is a PNP general-purpose bipolar junction transistor used for low-power amplification and switching in discrete analog and digital circuits, with V_CEO = 40 V, I_C = 200 mA continuous, h_FE = 30–150 (at I_C = 0.1–100 mA), and TO-92 package. It serves in signal inversion, level shifting, and load switching applications up to 100 MHz small-signal gain bandwidth.

For engineers reviewing the 2N3905TAR datasheet, pinout, applications, or equivalent options, key selection criteria include its PNP polarity, 40 V breakdown rating, 200 mA collector current capability, thermal resistance of 200 °C/W (junction-to-ambient), and verified performance in linear amplification and saturated switching modes.

Technical Context

The 2N3905TAR operates as a silicon PNP BJT with fixed-emitter bias topology, supporting common-emitter, common-base, and common-collector configurations. Its DC current gain (h_FE) varies from 30 at 100 mA to 150 at 0.1 mA, and its small-signal h_fe reaches 200 at 1 mA/10 V, enabling stable mid-band amplification.

Switching behavior is characterized by t_d = 35 ns, t_r = 35 ns, t_s = 200 ns, and t_f = 60 ns under specified pulse conditions (V_CC = 3.0 V, I_CS = 10 mA). Saturation voltages are V_CE(sat) ≤ 0.40 V and V_BE(sat) ≤ 0.95 V at I_C = 50 mA/I_B = 5 mA, confirming reliable on-state conduction.

Key Specifications

Pinout & Package

2N3905TAR is housed in a through-hole TO-92 package (3-lead, plastic case) with standardized lead orientation: Emitter (E), Base (B), Collector (C) from left to right when viewing the 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 MPSA56 and BC557, the 2N3905TAR offers balanced performance for cost-sensitive, medium-speed PNP switching and amplification-delivering sufficient gain, noise, and speed without over-specifying voltage or current capacity.

Availability

2N3905TAR is available at Aetrix Electronics and suitable for audio preamplification, discrete logic interfacing, relay driving, and current mirror reference applications requiring stable component supply and long-term industrial availability.

Supply support for 2N3905TAR 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 U.S.-based semiconductor company specializing in power management, analog, and discrete components before its acquisition by ON Semiconductor in 2016.

The 2N3905TAR belongs to Fairchild's legacy general-purpose transistor family, designed for broad utility in educational, prototyping, and industrial control circuits where reliability, consistency, and ease of use are prioritized.

FAQ

What is the pin configuration of the 2N3905TAR?

The 2N3905TAR uses a standard TO-92 package with Emitter (E), Base (B), and Collector (C) arranged left-to-right when viewing the flat side with leads pointing downward. This E-B-C order is confirmed in Fairchild's Rev A datasheet and matches industry-standard PNP pinout conventions for through-hole transistors.

Is the 2N3905TAR RoHS compliant?

Yes, the 2N3905TAR is RoHS compliant per Fairchild's product change notices and packaging documentation. It contains no lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB), or polybrominated diphenyl ethers (PBDE), meeting EU Directive 2011/65/EU requirements for restricted substances.

Can the 2N3905TAR replace an NPN transistor like the 2N3904?

No, the 2N3905TAR cannot directly replace the 2N3904 because it is a PNP device while the 2N3904 is NPN - polarity reversal requires circuit redesign including bias network inversion and signal path reorientation. The 2N3905TAR functions as a high-side switch or inverted amplifier, unlike the low-side NPN operation of the 2N3904.

What is the maximum operating frequency for small-signal amplification with the 2N3905TAR?

The 2N3905TAR achieves h_fe = 200 at f = 100 MHz and I_C = 1.0 mA/V_CE = 10 V, indicating usable small-signal gain up to approximately 100 MHz. Its f_T is estimated at 300 MHz, but practical amplification bandwidth is constrained by layout parasitics and bias stability in real-world implementations.

Does the 2N3905TAR support pulsed operation beyond its DC ratings?

Yes, the 2N3905TAR supports pulsed operation with peak currents exceeding 200 mA, provided pulse width ≤ 300 µs and duty cycle ≤ 2.0%, as validated in Fairchild's switching characteristics test conditions. Thermal limits must still be observed using R_θJA = 200 °C/W and junction temperature not exceeding +150°C.