Diodes Incorporated BCX38C

Overview

BCX38C from Nexperia is an NPN silicon planar medium-power Darlington transistor with V_CEO = 60 V, DC current gain (h_FE) of 5000–10000 at I_C = 500 mA, P_tot = 1 W, and TO-92 package. It serves as a high-gain switching or linear amplification device in low-frequency power control stages, such as relay drivers and lamp dimmers.

For engineers reviewing the BCX38C datasheet, BCX38C pinout, BCX38C application, or BCX38C equivalent, key selection criteria include verified h_FE range at 500 mA, V_CE(sat) ≤ 1.25 V under I_B = 8 mA drive, thermal derating behavior up to +200°C junction temperature, and TO-92 mechanical compatibility with legacy E-line footprints.

Technical Context

The BCX38C implements a monolithic Darlington pair structure with integrated base-emitter resistor network absent - requiring external base drive. Its high h_FE enables low-base-current switching of loads up to 800 mA while maintaining V_CE(sat) ≤ 1.25 V at I_C = 800 mA / I_B = 8 mA.

Designed for operation up to T_j = +200°C, it features V_CEO(sus) = 60 V under open-base conditions and supports pulse currents up to 2 A with duty-cycle-dependent SOA compliance. Thermal resistance R_th(j-a) is 175°C/W (typical) in free-air mounting.

Key Specifications

Pinout & Package

BCX38C is housed in a standard TO-92 plastic package (E-Line compatible), with leads arranged in emitter-base-collector (E-B-C) order when viewed from the flat side with leads downward.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN Darlington transistor applications.

Compared with BCX38B and MJD127, the BCX38C delivers optimal balance of ultra-high gain, TO-92 form factor, and 1 W thermal capability - making it uniquely suitable for space-constrained, low-base-drive, medium-power switching where gain stability at 500 mA matters most.

Availability

BCX38C is available at Aetrix Electronics and suitable for relay drivers, lamp dimmers, DC motor regulators, and thermal cut-off switches requiring stable component supply across industrial control, building automation, and appliance design programs.

Supply support for BCX38C 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

Nexperia is a global semiconductor expert focused on essential semiconductors, delivering high-performance, reliable components for automotive, industrial, and consumer applications.

The BCX38C belongs to Nexperia's general-purpose bipolar transistor product line, engineered for robust, cost-effective medium-power switching in legacy and new-design through-hole applications.

FAQ

Is BCX38C pin-compatible with BCX38A and BCX38B?

Yes - all three variants share identical TO-92 package, E-B-C lead assignment, and absolute maximum ratings. Only DC current gain differs: BCX38A (500–1000), BCX38B (2000–4000), BCX38C (5000–10000). No layout change is needed for substitution.

What is the recommended base resistor value for switching an 800 mA load?

With h_FE(min) = 5000 and I_C = 800 mA, minimum required I_B = 160 µA. For reliable saturation, target I_B ≥ 8 mA (50× min). At 3.3 V MCU output, R_B ≈ (3.3 V − 1.8 V)/8 mA = 188 Ω; use 180 Ω standard value.

Can BCX38C be used in linear amplifier mode?

Yes - its specified h_FE and V_CE(sat) are characterized at V_CE = 5 V, supporting Class-A or AB operation. However, P_tot = 1 W limits usable quiescent power; thermal design must ensure T_j stays below +200°C at worst-case ambient.

Does BCX38C have built-in base-emitter resistors?

No - BCX38C is a bare Darlington pair without integrated bias resistors. External base drive circuitry (e.g., series resistor, pull-down resistor) must be provided, unlike devices designated "pre-biased" (e.g., PBSS4041).