onsemi BD242TU

Overview

BD242TU from Fairchild Semiconductor is a PNP epitaxial silicon power transistor in TO-220 package, rated for -45 V V_CEO, -3 A continuous collector current, and 40 W collector dissipation at T_C=25°C, used in medium-power linear regulation and switching applications such as DC motor control and power supply output stages.

For engineers reviewing the BD242TU datasheet, pinout, applications, or equivalent options, key selection criteria include verified V_CEO(sus) = -45 V, h_FE ≥25 at I_C = -1 A, V_CE(sat) ≤ -1.2 V at I_C = -3 A/I_B = -0.6 A, and TO-220 thermal mounting compatibility.

Technical Context

The BD242TU operates as a medium-power PNP bipolar junction transistor with fixed gain structure optimized for linear amplification and hard-switching duty. Its V_CEO = -45 V and V_CER = -55 V define safe operating area boundaries under open-base and reverse-biased base conditions respectively.

Designed for complementary use with BD241TU, it supports Class AB audio output stages and relay drivers requiring robust DC current handling and stable h_FE across -1 A to -3 A range, with guaranteed V_BE(on) = -1.8 V ensuring predictable base drive requirements.

Key Specifications

Pinout & Package

BD242TU uses the standard TO-220 package with metal tab connected to collector, enabling direct heatsink mounting. Package outline conforms to JEDEC TO-220AB mechanical dimensions (15.90 mm × 10.08 mm × 4.50 mm height).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD242G and BD242C, the BD242TU offers optimal balance of through-hole manufacturability, 40 W thermal capacity, and -45 V rating for 24 V industrial control-making it preferable where legacy through-hole assembly and moderate voltage headroom are prioritized.

Availability

BD242TU is available at Aetrix Electronics and suitable for DC motor control, linear power supply regulation, relay driving, and audio output stages requiring stable component supply and long-term industrial availability.

Supply support for BD242TU 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 BD242TU belongs to Fairchild's BD24x PNP transistor family, designed specifically for medium-power linear and switching applications requiring ruggedness, predictable gain, and TO-220 thermal performance.

FAQ

What is the maximum continuous collector current rating for BD242TU?

The BD242TU has a maximum continuous collector current (I_C) rating of -3 A at T_C = 25°C. This value assumes proper heatsinking; derating is required above 25°C case temperature per the specified thermal resistance curve. The BD242TU must not exceed this current in DC or high-duty-cycle pulse operation to avoid thermal runaway or secondary breakdown.

Is BD242TU pin-compatible with BD241TU?

Yes, BD242TU is pin-compatible with BD241TU as a complementary pair: both use identical TO-220 package with Base–Collector–Emitter pinout (1–2–3). This allows direct substitution in push-pull or complementary symmetry circuits without PCB modification, though polarity reversal must be observed in schematic implementation.

What is the guaranteed minimum DC current gain (h_FE) for BD242TU?

The BD242TU guarantees h_FE ≥25 at V_CE = -4 V and I_C = -1 A, and ≥10 at I_C = -3 A. These values are measured under controlled test conditions and represent minimums across the production lot; actual units often exceed these figures, but design margins should be based on the specified minima.

Can BD242TU be used in switching power supplies?

Yes, BD242TU is qualified for switching applications including offline SMPS auxiliary supplies and DC-DC converter output stages. Its -45 V V_CEO, -1.2 V V_CE(sat), and fast minority-carrier lifetime support efficient hard-switching up to ~50 kHz, provided gate/base drive is optimized for saturation and storage time.

Does BD242TU have an insulated package variant?

No, the standard BD242TU uses non-insulated TO-220 with collector-connected metal tab. For insulated mounting, external mica or silicone washer isolation is required. Fairchild did not release an official insulated variant (e.g., TO-220FP) for the BD242TU; alternative parts like MJD242G offer different thermal paths but no inherent insulation.