onsemi BD240B

Overview

BD240B from ON Semiconductor is a PNP epitaxial silicon power transistor in TO-220 package, rated for -80 V V_CEO, -90 V V_CER, -2 A DC collector current, 30 W power dissipation at T_C = 25°C, and 150°C maximum junction temperature. It serves as a medium-power linear amplifier or switching device in complementary pair configurations with BD239B.

For engineers reviewing the BD240B datasheet, pinout, applications, or equivalent options, key selection criteria include V_CEO/V_CER rating margin, h_FE consistency at I_C = -1 A, V_CE(sat) under forced β = 5, thermal derating above 25°C, and TO-220 mechanical mounting compatibility.

Technical Context

The BD240B operates as a medium-power PNP bipolar junction transistor optimized for linear amplification and hard-switching applications. Its design supports stable DC current gain (h_FE ≥15 at I_C = -1 A) and low saturation voltage (V_CE(sat) ≤ -0.7 V at I_C = -1 A, I_B = -0.2 A), enabling efficient operation in Class AB audio stages and relay drivers.

It features a rugged epitaxial base structure with specified breakdown limits: V_CEO(sus) = -80 V (I_C = -30 mA, I_B = 0), V_ER = -5 V, and guaranteed leakage (I_CEO ≤ -0.3 mA at V_CE = -60 V). Thermal performance is defined by T_J(max) = 150°C and T_STG = -65 to 150°C.

Key Specifications

Pinout & Package

BD240B is housed in a through-hole TO-220 package with standard 3-pin configuration (1: Base, 2: Collector, 3: Emitter), featuring an electrically isolated metal tab tied to the collector for direct heatsink mounting and thermal management.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BD240B, MJD243G offers higher voltage/current but demands SMT redesign, while BD241C provides higher V_CEO and h_FE in the same TO-220 footprint-making it a drop-in performance upgrade where available.

Availability

BD240B is available at Aetrix Electronics and suitable for audio amplifier design, motor control systems, relay interface circuits, and linear regulator implementations requiring stable component supply across prototyping, pilot production, and long-lifecycle industrial programs.

Supply support for BD240B 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

ON Semiconductor is a global semiconductor supplier delivering energy-efficient, high-performance silicon solutions for automotive, industrial, cloud computing, medical, and IoT applications.

The BD240B belongs to ON Semiconductor's legacy power bipolar transistor portfolio, engineered for robust medium-power linear and switching applications where reliability, thermal stability, and complementary pairing are essential.

FAQ

What is the maximum collector-emitter voltage rating for BD240B?

The BD240B has a maximum collector-emitter voltage rating (V_CEO) of -80 V at T_C = 25°C. This rating applies under open-base conditions and defines the upper limit for safe DC or pulse operation before avalanche onset. Exceeding this voltage risks irreversible breakdown, especially at elevated temperatures where derating is required per the datasheet thermal curves.

Does BD240B have a built-in base-emitter resistor?

No, the BD240B is a standard discrete PNP bipolar junction transistor without any integrated base-emitter resistors. It requires external base drive circuitry-including current-limiting resistors-to establish proper biasing for linear or switching operation. This architecture provides full design flexibility but places responsibility on the user to size base components correctly for target h_FE and switching speed.

Can BD240B be used as a direct replacement for BD240A?

No, BD240B is not a direct replacement for BD240A due to differing voltage ratings: BD240A has V_CEO = -60 V and V_CER = -70 V, while BD240B is rated at -80 V and -90 V respectively. Substituting BD240B into a BD240A design is generally safe if voltage margins allow, but replacing BD240B with BD240A risks overvoltage failure in circuits operating near the -60 V limit.

What is the thermal resistance from junction to case for BD240B?

The BD240B datasheet does not specify R_θJC directly, but its TO-220 package and 30 W P_C rating at T_C = 25°C imply an approximate R_θJC of 0.83°C/W. This value is derived from ΔT = P × R_θJC, where maximum allowable junction-to-case temperature rise is 150°C − 25°C = 125°C. Actual thermal performance depends on heatsink quality, mounting pressure, and thermal interface material.

Is BD240B suitable for high-frequency switching applications?

The BD240B is not optimized for high-frequency switching; its transition frequency (f_T) is not specified in the provided documentation, and its charge storage characteristics favor medium-speed linear and switching use up to ~100 kHz. For PWM motor control or SMPS above 50 kHz, devices with documented f_T, lower C_ob, and faster t_f/t_r (e.g., MJD243G or NSS12201LT1G) are more appropriate than BD240B.