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BC548 Transistor Introduction

BC548 is another widely used general-purpose transistor, which also has many excellent characteristics. It can be used in its electronic circuits, and it can handle a maximum current of 500 mA. Enough to drive many other components, such as ICs, other transistors, parts of circuits, relays, LEDs, etc.

What is BC548 Transistor

BC548 is an NPN transistor, so when the base pin is grounded, the collector and emitter will remain disconnected (reverse bias); when the signal is supplied to the base pin, the collector and emitter will be closed (forward bias). The gain value of BC548 is 110 to 800, which determines the amplification capacity of the transistor. The maximum current flowing through the collector pin is 500mA, so we can not use the transistor connection to consume more than 500mA load. In order to bias the transistor, we have to supply current to the base pin, which should be limited to 5mA.

The transistor has four different part numbers, such as BC548, bc548a, bc548b and bc548c. The only difference between them is their DC current gain value. For example, BC548 current gain value is 110 to 800, bc548a is 110 to 220, bc548b is 200 to 450, bc548c is 420 to 800.

When the transistor is fully biased, it allows a maximum current of 500 mA to flow through the collector and emitter. This stage is called saturation region, and the typical voltage allowed for cross collector emitter (V ­ CE) or base emitter (v be) is 200 and 900 MV respectively. When the base current is removed, the transistor is completely cut off. This stage is called cut-off region, and the base emitter voltage may be about 660 MV.

BC548 datasheet

BC548 Pinout &Configuration

BC548 has three terminals, as shown in the table.

Pin NumberPin NameDescription
1CollectorCurrent flows in through collector
2BaseControls the biasing of transistor
3EmitterCurrent Drains out through emitter
BC548 Pinout &Configuration

BC548 Features

  1. Package Type: TO-92
  2. Transistor Type: NPN
  3. Max Collector Current(IC): 500mA (Continuous)
  4. Max Collector-Emitter Voltage (VCE): 30V
  5. Max Collector-Base Voltage (VCB): 30V
  6. Max Emitter-Base Voltage (VEBO): 5V
  7. Max Collector Dissipation (Pc): 625 miliWatt
  8. Max Transition Frequency (fT): 150 MHz
  9. Minimum & Maximum DC Current Gain (hFE): 110 – 800
  10. Max Storage & Operating temperature Should Be: -55 to +150 Centigrade

BC548 equivalent transistor

  • The BC548 equivalent transistors are: 2N2222, 2N3904, BC547, BC549, BC550
  • The BC548 pnp complementary is: BC558

How does a BC548 transistor work?

As mentioned above, BC548 transistors can be used in many general applications. You can use it instead of other general-purpose transistors 2N3904, bc547, etc. as described above. Part of it can be used as a switch to drive the load below 500mA. For this size and type of transistor, 500 mA collector current is a good feature, so you can drive all kinds of loads in one electronic circuit at the same time. In addition, the transistor also has very good DC current gain and collector dissipation characteristics, so it is very suitable for use in the amplification and pre amplification stages of electronic circuits.

BC548 Transistor as switch


When the crystal tube is used as a switch, it operates in the saturation and cut-off regions as described above. As mentioned earlier, the transistor will be used as an off switch during forward bias and as a close switch during reverse bias, which can be achieved by providing the required current to the base pin. As mentioned before, the bias current shall be 5 Ma maximum. Any current greater than 5mA will kill the transistor. Therefore, a resistor is always connected in series with the base pin to limit the current. The resistance value (RB) of the resistor can be calculated using the following formula.


Where, the value of VBE should be 5V for BC548 and the Base current (IB depends on the Collector current (IC). The value of IB should not exceed 5mA.

BC548 Applications

  • Sensor Circuits
  • Audio Preamplifiers
  • Audio Amplifier Stages
  • Switching Loads under 500mA
  • Darlington Pairs

That’s all for today. Hope you enjoyed this article. However, if you have doubts or have any questions about this, you can contact me in the comments section below. I’ll be happy to help you as best I can. Let us know your feedback and suggestions at any time, they allow us to provide you with high-quality work that responds to your needs and expectations, and helps you continue to give back to our products. Thank you for reading this article.

3Celectrons also provide this kind of parts, if you are interested in, just contact us!

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