BDX35 NPN Switching Transistor Technical Summary

Overview

The BDX35 is a high-current NPN switching transistor housed in a TO-126 (SOT32) plastic package. Designed for robust performance in switching applications, this transistor is capable of handling currents up to 5 A and voltages up to 75 V. Its construction ensures reliable operation in a variety of electronic circuits, making it a versatile choice for designers and engineers.

The BDX35 is particularly well-suited for applications requiring efficient switching of moderate to high currents, such as power supplies, motor control, and relay drivers. Its NPN configuration allows for easy integration into standard circuit designs, while its TO-126 package provides a balance between thermal performance and physical size.

Features

• High Current Capability: Maximum collector current of 5 A, making it suitable for power switching applications.
• Moderate Voltage Rating: Collector-emitter voltage (V_CEO) of up to 75 V, enabling use in a wide range of circuit designs.
• Low Saturation Voltage: Ensures minimal power loss during conduction, improving overall efficiency.
• TO-126 Package: Robust plastic package (SOT32) with good thermal characteristics for reliable operation.
• NPN Polarity: Compatible with standard NPN transistor circuit configurations.
• Fast Switching Speed: Suitable for applications requiring rapid on/off transitions.

Applications

The BDX35 is widely used in electronic circuits where efficient switching of moderate to high currents is required. Some typical applications include:

• Power Supply Circuits: Used as a switching element in linear and switched-mode power supplies.
• Motor Control: Suitable for driving small to medium-sized motors in appliances and industrial equipment.
• Relay and Solenoid Drivers: Provides the necessary current to actuate relays and solenoids in control systems.
• Audio Amplifiers: Can be used in the output stages of audio amplifiers for driving speakers or other loads.
• Lighting Control: Used in circuits controlling incandescent or LED lighting systems.
• General Purpose Switching: Applicable in various electronic switching circuits where an NPN transistor is required.

Electrical Characteristics

The following table summarizes the key electrical characteristics of the BDX35 transistor under standard test conditions (unless otherwise specified):

Absolute Maximum Ratings

• Collector-Emitter Voltage (V_CEO): 75 V
• Collector-Base Voltage (V_CBO): 80 V
• Emitter-Base Voltage (V_EBO): 5 V
• Collector Current (I_C): 5 A
• Base Current (I_B): 2 A
• Total Power Dissipation (P_tot): 36 W (at T_case ≤ 25°C)
• Operating Junction Temperature (T_j): -55°C to +150°C
• Storage Temperature (T_stg): -55°C to +150°C

Thermal Characteristics

• Thermal Resistance, Junction to Case (R_thJC): 3.125 °C/W
• Thermal Resistance, Junction to Ambient (R_thJA): 62.5 °C/W

On Characteristics

• DC Current Gain (h_FE): 20 - 250 (at I_C = 2 A, V_CE = 2 V)
• Collector-Emitter Saturation Voltage (V_CE(sat)): 0.5 V (max) (at I_C = 2 A, I_B = 0.2 A)
• Base-Emitter Saturation Voltage (V_BE(sat)): 1.2 V (max) (at I_C = 2 A, I_B = 0.2 A)

Small Signal Characteristics

• Transition Frequency (f_T): 3 MHz (min) (at I_C = 0.5 A, V_CE = 10 V)
• Output Capacitance (C_obo): 100 pF (max) (at V_CB = 10 V, f = 1 MHz)

Package Information

The BDX35 is packaged in a TO-126 (SOT32) plastic package, which provides a good balance between thermal performance and physical size. The package dimensions and pin configuration are as follows:

Package Dimensions

• Package Type: TO-126 (SOT32)
• Mounting Style: Through-hole
• Weight: Approximately 1.1 g
• Lead Material: Copper alloy
• Lead Finish: Tin-plated

Mechanical Drawing

The following are the key dimensions of the TO-126 package (all values in millimeters):

• Total Height: 9.65 mm (max)
• Body Length: 10.4 mm (max)
• Body Width: 4.6 mm (max)
• Lead Length: 19 mm (nominal)
• Lead Spacing: 5.45 mm (between centers)

Pin Configuration

The TO-126 package has three leads with the following pinout when viewing the flat side of the package with leads pointing downward:

• Pin 1 (Left): Collector
• Pin 2 (Center): Base
• Pin 3 (Right): Emitter

Thermal Considerations

Proper thermal management is crucial when using the BDX35 in high-current applications. The following guidelines should be observed:

• For continuous operation at high currents, a heatsink should be used to maintain the junction temperature within safe limits.
• The thermal resistance from junction to ambient (R_thJA) can be significantly reduced by proper heatsinking.
• When mounting the transistor, ensure good thermal contact between the package and heatsink using appropriate thermal interface materials.
• In high-frequency switching applications, consider the thermal time constants to prevent localized overheating.

Reliability and Quality

The BDX35 is manufactured using high-quality processes and materials to ensure reliable operation:

• Manufactured in accordance with