BC640 PNP Transistor: Features, Package and Other Details

27 September 2023 14

Ⅰ. Overview of BC640

Ⅱ. Symbol and footprint of BC640

Ⅲ. Technical parameters

Ⅳ. Features of BC640

Ⅴ. Pinout and package of BC640

Ⅵ. Application of BC640

Ⅶ. How to optimize the performance of BC640 transistor?

Ⅰ. Overview of BC640


The BC640 transistor is a low-power PNP triode. With a power dissipation capability of 625 milliwatts, the BC640 is more than capable of handling moderate power requirements efficiently. Furthermore, it can sustain a continuous collector current of negative 500 milliamperes, demonstrating its reliability in maintaining consistent electrical flow. With its user-friendly design, this transistor features three pins and is specifically engineered for through-hole installation, simplifying the assembly process. Its compact physical dimensions, which include a length of 5.2 millimeters, a width of 4.19 millimeters, and a height of 5.33 millimeters, make it easy to integrate into compact electronic circuits while conserving space.

Replacement and equivalent:



• MPS4250G


Ⅱ. Symbol and footprint of BC640


Ⅲ. Technical parameters


Ⅳ. Features of BC640

• High performance, low power 8-bit microcontroller

• High frequency and high speed performance

• Has a battery backup register to protect important data from loss when the main power fails

• Has high characteristic frequency (fT=100 MHz) and DC amplification factor (hFE=40~160)

• At a specific ambient temperature (Ta=25°C), the power dissipation of this transistor is 1 W

• The maximum collector current is 1 A; the maximum collector and emitter withstand voltage is 80 V; the maximum emitter and base withstand voltage is 5 V.

Ⅴ. Pinout and package of BC640

1. Pinout of BC640


BC640 is a commonly used NPN bipolar junction transistor (BJT) with three pins, namely emitter (E), collector (C) and base (B).

Pin1 (Emitter) : The emitter terminal is the output of the transistor. When the transistor is in the active region, current flows from the emitter terminal. It is usually connected to the load or circuit we want to control.

Pin2 (Collector): This is the power pin. When the transistor is in the active region, current flows into the collector terminal. It is usually connected to the positive supply voltage.

Pin3 (Base): This is the control input of the transistor. The base terminal controls the flow of current between the collector and emitter terminals. By applying a small current or voltage to the base, it controls the flow of a larger current from the collector to the emitter.

2. Package of BC640

The BC640 transistor is packaged in TO-92. This small three-lead package is designed to be simple and easy to handle, and is suitable for through-hole soldering on a PCB.

Ⅵ. Application of BC640

• Signal Modulation: It can be used in Amplitude Modulation (AM) and Frequency Modulation (FM) circuits where signal modulation is required.

• Voltage Regulation: In voltage regulator circuits, BC640 can be used to control the output voltage by regulating the current flowing through the load.

• Signal buffering: It can be used as a buffer to isolate one part of a circuit from another, preventing loading effects and ensuring signal integrity.

• Oscillators: BC640 can be used in oscillator circuits to generate high frequency signals, such as radio frequency communications, signal generators and clock circuits.

• Audio Amplification: It can be used in audio amplifier circuits to amplify audio signals in applications such as radios, amplifiers and intercom systems.

• Switching: BC640 can be used as a switching transistor in digital or control applications. When used as a switch, it can control the flow of current between two terminals (collector and emitter) based on the voltage applied to its base terminal. It can be used to turn other components such as LEDs, relays, or other transistors on or off.

Ⅶ. How to optimize the performance of BC640 transistor?

First, choose high-quality materials. The material of the BC640 triode will also affect its performance. During the manufacturing process, we need to use high-quality materials and advanced process technology to improve the stability and reliability of the triode.

Second, select the configuration components rationally. The performance of the BC640 transistor is affected by other components in the circuit such as resistors, capacitors, etc. Therefore, we need to reasonably select configuration components based on actual circuit requirements.

Third, optimize the design of the transistor itself. We can optimize the junction structure of the triode, adopt new materials and other measures to improve the triode's amplification, frequency response and other performance indicators.

Fourth, set up the bias circuit reasonably. The settings of the bias circuit can affect the working status and performance of the triode. By properly setting the bias circuit, we can optimize the static and dynamic performance of the triode.

Frequently Asked Questions

1. What is a BC640 transistor?

A BC640 is a small-signal NPN bipolar junction transistor (BJT). It belongs to the BC6xx series of transistors and is typically used for amplification and switching applications in electronic circuits.

2. What is the operating temperature range of BC640?

The operating temperature of BC640 ranges from -55°C to 150 °C.

3. What is the equivalent of BC640?

You can replace the BC640 with the BC635, BC640TA, MPS4250G or PN4250.

4. Can BC640 transistors be used in high-power applications?

No, BC640 transistors are not suitable for high-power applications due to their low power dissipation rating and relatively low collector current capability. They are best suited for low to moderate power applications.