1. General Information

️· Type: NPN Bipolar Junction Transistors (BJTs)
️· Variants: BD241, BD241A, BD241B, BD241C (each variant has slightly different performance characteristics - see below)
️· Package: TO-220
️· Datasheet Revision: September 2012

2. Key Electrical Characteristics (Highlights - See Datasheet for Complete Table)

️· VCEO (Collector-Emitter Voltage): 45V - 100V (varies by variant - BD241 is 45V, BD241C is 100V)
️· IC (Collector Current): 3A (Maximum)
️· hFE (DC Current Gain): A wide range (25 to 10 for BD241) This is highly variable. It specifies ranges for different current levels (1A and 3A).
️· hFE (Small Signal Current Gain @ 1MHz, IC=0.5A, VCE=10V):
- BD241: 3
- BD241A, B, and C: Not specified but likely similar.
️· VCE(sat) (Collector-Emitter Saturation Voltage): Around 1.2V (but variant dependent).
️· VBE(on) (Base-Emitter Voltage (ON)): Around 1.8V
️· Pulse Testing Conditions: Pulse Width ≈ 300 µs, Duty Cycle ∠ 2.0% (Important for pulsed applications - measurements under these conditions will differ from DC measurements)

3. Variant Differences

️· BD241: The "base" model. Generally, has the lowest voltage and current ratings among the variants.
️· BD241A: A slight enhancement over the BD241.
️· BD241B: An enhancement over BD241A.
️· BD241C: The highest voltage variant. It has the highest maximum ratings.

4. Mechanical Dimensions (TO-220 Package)

️· The datasheet provides detailed dimensional specifications for the TO-220 package. This is essential for PCB layout and mechanical design.

5. Pinout

️· Pin 3: Emitter
️· Pin 2: Collector
️· Pin 1: Base

Important Considerations & Notes

️· Current Gain (hFE) Variation: The DC current gain is very variable. Expect significant variation even within the same batch of transistors. This is a characteristic of BJTs.
️· Power Dissipation: The datasheet *doesn't* explicitly state the maximum power dissipation, but it's a critical parameter to consider in your design. It's likely to be around 10-15W, but a more precise value is needed to prevent overheating.
️· Pulsed Measurements: The pulsed testing conditions significantly influence measured values like current gain and saturation voltage. Make sure to consider these conditions if your application involves pulsed operation.
️· Small Signal Current Gain (hFE) at 1 MHz: While specified at 1 MHz for the BD241, note that the performance at this frequency might not be ideal for all applications.