BD135 Transistor (NPN, 45V, 1.5A)

Description

BD135 Transistor (NPN, 45V, 1.5A)

The BD135 is a NPN bipolar junction transistor (BJT) designed for medium-power switching and amplification applications. It is widely used in electronic circuits for driving loads, signal amplification, and switching purposes. This transistor has good current and voltage ratings, making it suitable for a variety of applications in analog and digital electronics.

Key Features:

1. Type:
   • The BD135 is an NPN type transistor, meaning it has negative (N) type material sandwiched between two positive (P) type materials.
2. Collector-Emitter Voltage (Vceo):
   • The BD135 can withstand a maximum collector-emitter voltage (Vceo) of 80V, making it suitable for medium-voltage applications.
3. Collector Current (Ic):
   • The maximum collector current (Ic) is 1.5A, meaning it can handle moderate current levels, which makes it versatile for controlling small motors, relays, and other loads.
4. Power Dissipation:
   • The transistor can dissipate up to 30W, allowing it to operate at higher power levels without overheating.
5. DC Current Gain (hFE):
   • The BD135 provides a current gain (hFE) typically in the range of 40 to 320. The current gain is an important characteristic for amplification applications, as it indicates how much the transistor amplifies the input signal.
6. Package Type:
   • It is typically available in a TO-220 package, which is a through-hole package commonly used for power transistors. The TO-220 package allows for better heat dissipation, making it suitable for medium to high-power applications.
7. Frequency Response:
   • The BD135 has a transition frequency (ft) of around 250 MHz, allowing it to function well in high-frequency applications like audio amplifiers and RF circuits.

Applications:

1. Switching Applications:
   • The BD135 can be used in switching circuits to control moderate loads such as relays, small motors, or LEDs. It is typically used for high-speed switching in digital and analog circuits.
2. Amplification:
   • The BD135 is widely used in amplifier circuits for audio and RF signals. It is often used in low-power audio amplifiers or class AB audio power amplifiers, as it can provide good amplification with a current gain suitable for these applications.
3. Power Amplifiers:
   • It is used in power amplifier circuits, especially in audio amplifiers, where it helps to drive loudspeakers or other output devices.
4. Voltage Regulators:
   • The BD135 can be used in voltage regulator circuits as part of a linear voltage regulator to provide stable output voltage.
5. Relay Drivers:
   • It is commonly used in relay driver circuits for switching heavier loads in response to smaller control signals.
6. Switch Mode Power Supply (SMPS):
   • The BD135 can be used in SMPS circuits for controlling the switching elements in the power supply and providing efficient power conversion.
7. LED Drivers:
   • The transistor can be used to drive high-power LEDs that require more current than a microcontroller or low-power logic circuit can supply.

Advantages:

1. Medium Power Handling:
   • With a maximum collector current of 1.5A, the BD135 can drive moderate loads such as small motors, relays, or other electronic devices.
2. High Voltage Rating:
   • The 45V collector-emitter voltage rating makes the BD135 suitable for applications in medium-voltage circuits.
3. Good Frequency Response:
   • With a transition frequency of 250 MHz, it is suitable for high-frequency applications, including audio amplification and RF circuits.
4. Power Dissipation:
   • The 30W power dissipation allows the transistor to handle higher-power applications without overheating, making it more robust for amplifiers and high-power switching circuits.
5. Wide Availability and Cost-Effective:
   • The BD135 is widely available, cost-effective, and suitable for both hobbyists and professional circuit designers.

Disadvantages:

1. Limited Current Handling:
   • The 1.5A current rating limits its use in high-power applications. For circuits that require higher current, other transistors or MOSFETs with higher current ratings would be more suitable.
2. Medium Voltage Rating:
   • The 45V maximum voltage makes it unsuitable for applications that require higher voltage ratings. For higher voltage applications, a transistor with a higher voltage rating would be needed.
3. Limited Switching Speed:
   • While it has a reasonable frequency response, it may not be suitable for applications requiring extremely high-speed switching compared to more modern MOSFETs or bipolar junction transistors with faster switching characteristics.

Pinout (TO-220 Package):

1. Pin 1 (Base – B):
   • The base of the NPN transistor, where the small control current is applied to turn the transistor on.
2. Pin 2 (Collector – C):
   • The collector of the NPN transistor, where the larger current flows from the power supply through the load and into the transistor.
3. Pin 3 (Emitter – E):
   • The emitter of the NPN transistor, where the current exits the transistor to return to the ground or the negative side of the power supply.

How to Use the BD135:

1. Switching Circuit:
   • To switch a load, a small current is applied to the base through a current-limiting resistor. This allows a larger current to flow from the collector to the emitter and power the load.
2. Amplification Circuit:
   • In an amplifier circuit, the BD135 amplifies an input signal applied to the base. The collector current varies according to the input signal, producing an amplified output.
3. Current Limiting:
   • It is essential to use base resistors to limit the current flowing into the base, ensuring the transistor operates within safe limits.
4. Heat Management:
   • Due to its power dissipation of up to 30W, the BD135 may require proper heat sinking to prevent it from overheating in high-power applications.