Onsemi BD244CG Bipolar Power Transistor: Datasheet, Pinout, and Application Circuits

The BD244CG from Onsemi is a robust PNP bipolar junction transistor (BJT) designed for medium-power linear and switching applications. As a member of the longstanding BD series, it is renowned for its durability and high current-handling capability, making it a popular choice in power supply circuits, audio amplifiers, and as a driver for larger loads. This article provides a detailed overview of its datasheet specifications, pinout configuration, and common application circuits.

Datasheet Overview and Key Specifications

The BD244CG is a complementary PNP type to the NPN BD243C transistor. It is housed in a TO-220 package, which facilitates easy mounting on a heatsink for efficient thermal management. Key absolute maximum ratings from its datasheet define its operational limits:

Collector-Emitter Voltage (VCEO): -45 V

Collector Current (IC): -6 A (continuous)

Base Current (IB): -3 A

Power Dissipation (PTOT): 65 W (at case temperature ≤ 25°C)

Junction Temperature (TJ): 150 °C

Its DC current gain (hFE) is categorized into four groups (CG, BG, etc.), with the BD244CG offering a gain range of 35 to 100 at a collector current of 3 A and VCE of -4 V. This relatively high gain for a power transistor simplifies drive circuit design. The transistor also features a low collector-emitter saturation voltage (VCE(sat)), typically -1.5 V at IC = -3 A and IB = -0.6 A, which minimizes power loss during the on-state in switching applications.

Pinout Configuration

Correctly identifying the pins is crucial for circuit operation and preventing damage. The standard pinout for the TO-220 package of the BD244CG is as follows:

1. Emitter (E): This pin is typically connected to the positive supply rail (for a PNP) or ground, depending on the circuit configuration.

2. Collector (C): The load (e.g., a motor, relay, or speaker) is usually connected between this pin and the supply voltage.

3. Base (B): This is the control pin. A negative current (relative to the emitter) applied here switches the transistor on.

Important: Always refer to the physical component, as the pin order can sometimes vary by manufacturer. The flat face of the TO-220 package with the markings should be facing you for the standard pinout.

Common Application Circuits

1. Linear Series Voltage Regulator

The BD244CG is well-suited as a pass transistor in linear voltage regulator circuits. In this configuration, it handles the high output current, while a low-power op-amp or zener diode provides the voltage reference and error amplification. The transistor dissipates the excess power as heat, making a sufficient heatsink mandatory.

2. Power Amplifier Output Stage

In audio amplifier designs, the BD244CG (PNP) is often used in a push-pull configuration with its NPN complement (e.g., BD243C). This setup allows one transistor to amplify the positive half of the audio signal while the other handles the negative half, resulting in efficient and high-fidelity power delivery to a speaker.

3. High-Current Switch

A fundamental application is using the BD244CG as a switch to control high-power devices like DC motors, solenoids, or lamps. A small signal from a microcontroller or logic IC (often buffered by a smaller transistor) is applied to the base to turn the load on or off. A flyback diode must be placed across an inductive load (like a motor or relay coil) to protect the transistor from voltage spikes generated when the current is suddenly interrupted.

4. Darlington Pair Driver

For applications requiring even higher current gain, the BD244CG can be used as the output transistor in a Darlington pair. A smaller PNP driver transistor is connected to its base, resulting in a combined gain that is the product of the gains of the two individual transistors. This allows a very tiny input current to control a very large output current.

ICGOODFIND Summary: The Onsemi BD244CG is a versatile and rugged PNP power transistor that excels in both linear amplification and high-speed switching roles. Its high current capacity of 6A and 65W power rating make it ideal for demanding applications in power management, audio, and motor control. Designers must prioritize adequate heatsinking and proper base driving to ensure reliable and efficient operation within its specified limits.

Keywords: Power BJT, PNP Transistor, TO-220 Package, Switching Circuit, Linear Amplifier.