onsemi BCX71G

Overview

BCX71G from Fairchild Semiconductor is a PNP epitaxial silicon general-purpose transistor in SOT-23 package, rated for -45 V V_CEO, -100 mA I_C, and 350 mW P_C, commonly used in low-power switching and linear amplification circuits in consumer and industrial control modules.

For engineers reviewing the BCX71G datasheet, pinout, applications, or equivalent options, key selection criteria include verified PNP polarity, SOT-23 footprint compatibility, h_FE range of 120–220 at I_C = -2 mA, V_CE(sat) ≤ -0.55 V at I_C = -50 mA, and guaranteed -5.0 V V_EBO rating.

Technical Context

The BCX71G operates as a discrete PNP bipolar junction transistor with fixed emitter-base and collector-base junctions optimized for medium-speed switching (t_ON = 150 ns, t_OFF = 800 ns) and low-noise analog operation (NF = 6 dB at 1 kHz). It exhibits defined saturation behavior under controlled base drive conditions (I_B = -0.25 mA / -1.25 mA).

Its electrical characteristics are specified at T_a = 25°C with strict derating above that temperature, and its SOT-23 package supports surface-mount assembly on dense PCB layouts while maintaining thermal dissipation up to 350 mW at ambient.

Key Specifications

Pinout & Package

SOT-23 plastic surface-mount package with gull-wing leads; standardized 3-pin footprint measuring 2.90 mm × 1.30 mm × 1.00 mm (L × W × H), compatible with automated pick-and-place and reflow soldering.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BCX71G, BC807-16 offers improved gain consistency but reduced saturation efficiency at high current, while MMBT3906 trades gain stability and power handling for broader availability and lower unit cost in low-duty-cycle applications.

Availability

BCX71G is available at Aetrix Electronics and suitable for LED driver circuits, level-shifting interfaces, low-power audio preamplifiers, and relay driver stages requiring stable component supply and long-term manufacturability.

Supply support for BCX71G 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 BCX71G belongs to Fairchild's general-purpose bipolar transistor product line, designed for cost-sensitive, space-constrained applications requiring reliable PNP switching and amplification performance in consumer and industrial electronics.

FAQ

What is the pin configuration of the BCX71G?

The BCX71G uses a standard SOT-23 package with pin 1 as Base, pin 2 as Emitter, and pin 3 as Collector. This arrangement is confirmed in the original Fairchild datasheet Rev. A1 (April 2002) and matches JEDEC MO-178AB mechanical specifications. The BCX71G must be mounted with correct orientation to ensure proper PNP biasing and avoid reverse connection damage.

Does the BCX71G support operation at elevated temperatures?

The BCX71G is rated for storage up to 150°C, but its electrical characteristics are specified at T_a = 25°C. Derating applies above this temperature: power dissipation decreases linearly beyond 25°C, and h_FE typically declines. For continuous operation above 70°C ambient, thermal analysis using the BCX71G's 350 mW P_C and package thermal resistance is required.

Can the BCX71G replace the BC557 in a circuit?

The BCX71G is not a direct replacement for the BC557 due to differences in package (SOT-23 vs. TO-92), pinout, and thermal performance. While both are PNP transistors with similar voltage ratings, the BCX71G's SOT-23 footprint and lower power dissipation (350 mW vs. 500 mW) require PCB redesign and thermal reassessment before substitution in any BC557-based design.

What is the typical noise figure of the BCX71G and under what conditions is it measured?

The BCX71G has a typical noise figure of 6 dB, measured at I_C = 0.2 mA, V_CE = 5 V, f = 1 kHz, and R_S = 2 kΩ. This value reflects its suitability for low-noise small-signal amplification, and appears in the "Electrical Characteristics" table of the official Fairchild BCX71G datasheet. Designers should maintain these bias conditions to achieve the stated BCX71G noise performance.

Is the BCX71G RoHS compliant?

The BCX71G was introduced prior to RoHS legislation (2006), and Fairchild's documentation does not declare RoHS compliance for this specific part number. Later equivalents such as the BC807 series are RoHS-compliant, but for BCX71G, compliance status depends on manufacturing date and lot traceability. Aetrix Electronics can provide material declarations upon request for specific BCX71G shipment batches.