STMicroelectronics BDX34C

Overview

BDX34C from STMicroelectronics is a complementary PNP silicon power Darlington transistor in TO-220 package, designed for high-current linear and switching applications such as motor control and power supply output stages. It features V_CEO = −100 V, I_C = −10 A, P_tot = 70 W at T_c ≤ 25 °C, R_thj-case = 1.78 °C/W, and h_FE ≥ 750 at I_C = −3 A.

For engineers reviewing the BDX34C datasheet, BDX34C pinout, BDX34C application, or BDX34C equivalent, key selection criteria include safe operating area (SOA) compliance at elevated case temperatures, Darlington base drive requirements (I_B ≤ −0.25 A), saturation voltage under load (V_CE(sat) ≤ −2.5 V @ I_C = −3 A), and thermal derating above 25 °C.

Technical Context

The BDX34C integrates an internal Darlington pair with integrated base-emitter resistors (R1 ≈ 10 kΩ, R2 ≈ 150 Ω), enabling simplified biasing and improved turn-off speed versus single bipolar transistors. Its monolithic epitaxial-base structure ensures stable h_FE across temperature and current ranges.

As a PNP device, it operates with negative voltage/current polarities relative to ground-referenced NPN counterparts (e.g., BDX33C). All absolute maximum ratings-including V_CBO = −100 V, I_CM = −15 A, and T_j(max) = 150 °C-are defined with sign conventions consistent with PNP polarity.

Key Specifications

Pinout & Package

BDX34C is housed in JEDEC-standard TO-220 plastic package with metal tab electrically connected to collector. Pin assignment (viewed from front, leads down): Pin 1 = Emitter, Pin 2 = Base, Pin 3 = Collector (tab).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP power Darlington switching applications.

Compared with MJD44H11T4, BDX34C offers superior thermal performance (1.78 vs. 3.0 °C/W) but requires through-hole assembly; versus BDX34B, it provides +25 % voltage margin critical for transient-heavy industrial environments.

Availability

BDX34C is available at Aetrix Electronics and suitable for DC motor control, linear power supply regulation, inductive load switching, and high-current relay driving requiring stable component supply across production lifecycles.

Supply support for BDX34C 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, specializing in power management, analog, microcontrollers, and discrete devices for industrial, automotive, and consumer markets.

The BDX34C belongs to ST's legacy high-power bipolar transistor family, engineered for robustness in industrial power conversion and electromechanical control where reliability under thermal stress and voltage transients is essential.

FAQ

Is BDX34C pin-compatible with BDX34B?

Yes-BDX34C and BDX34B share identical TO-220 package dimensions, pinout (Emitter-Base-Collector), and mechanical mounting. The only difference is V_CEO rating: −100 V for BDX34C versus −80 V for BDX34B. No PCB or heatsink redesign is needed for substitution.

What is the recommended base drive for saturation at 10 A collector current?

At I_C = −10 A, datasheet h_FE drops to ~200–300. To ensure hard saturation, apply I_B ≥ −50 mA (e.g., −5 V across 100 Ω). Avoid relying on minimum h_FE alone; use forced β = 20 for design margin.

Can BDX34C be used without a heatsink?

No-70 W P_tot requires active thermal management. At ambient 25 °C and no heatsink, junction temperature would exceed 150 °C with <1 W dissipation. Even at 1 A/10 V (10 W), a minimum 10 °C/W heatsink is required to maintain T_j < 125 °C.

Does BDX34C include an integrated antiparallel diode?

No-BDX34C is a bare PNP Darlington transistor without an integrated freewheeling diode. For inductive loads, an external fast-recovery diode (e.g., BYV26E) must be connected cathode-to-collector, anode-to-emitter to clamp flyback voltage.