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BC548 Transistor: Datasheet, Equivalent, Pinout [FAQ]

Author: Iggy Date: 5 Mar 2021  215

The BC548 is a NPN bipolar junction transistor.

BC548 is another general purpose widely used transistor that can be easily accessed from reputable electronic components store, this transistor also has lots of good features on the basis of which it can be used in their electronic circuit, it can handle a maximum current of 500mA which is sufficient to drive many other components such as ICS, other transistors, circuit portions, relays, LEDs, etc. The max collector dissipation of the device is 625 milliWatt, which is another good feature to use as a small amplifier.

This blog gives you a basic overview of the BC548 transistor, including its pin descriptions, features and specifications, alternative products, etc., to help you quickly understand what BC548 is all about.

We'll be glad to find that this blog can be useful for people who love electronic components.



BC548 Pinout

BC548 Advantage

BC548 Features and Specifications

BC548 Application

BC548 as Amplifier

BC548 as Switch

BC548 Replacement and Equivalent

BC548 Complementary Pairs

BC548 Equivalent Transistors

How to Safely Long Run BC548 in Circuit

Where to Use BC548

Component Datasheet


BC548 Pinout

The BC548 is supplied in a standard TO-92 3-pin package. The assignment of transistor elements (b,c,e) to leads, i.e. the "pinout", uses the same convention used by some - but not all - other TO-92 devices. As viewed in the top-right image, going from left to right, the pinout is as follows:

  • lead 1 (left in diagram) is the collector,
  • lead 2 is the base,
  • lead 3 is the emitter.

Sometimes the middle pin is supplied bent to form a triangle of leads (as found in TO-18 case transistors and, for example, the ZTX108-L) to match the pinout of the BC108 more exactly.

BC548 Transistor Pinout


Pin Number

Pin Name




The flow of current will be through the collector terminal. It is dented by “C”



This pin controls the transistor biasing. It is denoted by “B”



The current supplies out through the emitter terminal It is denoted by “E”


BC548 Advantage

bc548 transistor ic

BC548 NPN Transistor

BC548 is a NPN transistor so the collector and emitter will be left open (Reverse biased) when the base pin is held at ground and will be closed (Forward biased) when a signal is provided to base pin. BC548 has a gain value of 110 to 800, this value determines the amplification capacity of the transistor. The maximum amount of current that could flow through the Collector pin is 500mA, hence we cannot connect loads that consume more than 500mA using this transistor. To bias a transistor we have to supply current to base pin, this current (IB) should be limited to 5mA.

When this transistor is fully biased, it can allow a maximum of 500mA to flow across the collector and emitter. This stage is called Saturation Region and the typical voltage allowed across the Collector-Emitter (V­CE) or Base-Emitter (VBE) could be 200 and 900 mV respectively. When base current is removed the transistor becomes fully off, this stage is called as the Cut-off Region and the Base Emitter voltage could be around 660 mV.

BC548 Features and Specifications

Package Type: TO-92

Transistor Type: NPN

Max Collector Current(IC): 500mA (Continuous)

Max Collector-Emitter Voltage (VCE): 30V

Max Collector-Base Voltage (VCB): 30V

Max Emitter-Base Voltage (VEBO): 5V

Max Collector Dissipation (Pc): 625 miliWatt

Max Transition Frequency (fT): 150 MHz

Minimum & Maximum DC Current Gain (hFE): 110 – 800

Max Storage & Operating temperature Should Be: -55 to +150 Centigrade

The BC548 part number is assigned by Pro Electron, which allows many manufacturers to offer electrically and physically interchangeable parts under one identification. Devices registered to this Pro Electron number must have the following minimum performance characteristics:

  • Breakdown voltage, collector-to-emitter with base open-circuit VCEO = 30 V (see below)
  • Rated continuous collector current IC = 100 mA (Fairchild's BC548 at one time had a higher rating)
  • Rated total power dissipation Ptotal = 500 mW (some manufacturers may specify 625 mW - see below)
  • Transition frequency (gain-bandwidth product) ft = 150 MHz minimum (300 MHz typical)

BC548 Application

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

BC548 as Amplifier

A Transistors acts as an Amplifier when operating in Active Region. It can amplify power, voltage and current at different configurations.

Some of the configurations used in amplifier circuits are

  1.  Common emitter amplifier
  2.  Common collector amplifier
  3.  Common base amplifier

Of the above types common emitter type is the popular and mostly used configuration. When used as an Amplifier the DC current gain of the Transistor can be calculated by using the below formulae

DC Current Gain = Collector Current (IC) / Base Current (IB)

BC548 as Switch

The region responsible for a transistor to work as a switch are Saturation Region and the Cut-off Region. When we apply a high enough current at the base of the transistor, it makes a path for the collector current to go through the base towards the emitter.

In order to use the transistor as a switch, it must be driven into the saturation region with enough base current. And a transistor operates as a closed switch under the saturation region.

Transistor as a closed switch

Transistor as a closed switch

As soon as a positive signal (in form of voltage and current) is removed across the base of the transistor, the flow of electric current between the collector and emitter becomes zero. And the transistor behaves like an open switch under the cut-off region.

Transistor as an open switch

Transistor as an open switch

This simply implies if we apply signal (voltage/current) across the collector and emitter but not across the base, the transistor will not work. But a small signal across the base is enough to make it work.

BC548 Replacement and Equivalent

BC547, BC549, 2N2222, 2N3904, BC550 (Pin configuration of some transistors may different from BC548, check pin configuration before using or replacing in a circuit)

BC548 Complementary Pairs

The PNP counterparts of the BC546 to BC550 are the BC556 to BC560 respectively, i.e. the type numbers are higher by ten.


The BC558 is the PNP version of the BC548, and has higher voltage versions: BC556 and BC557, and lower noise versions: BC559 and BC560.

BC548 Equivalent Transistors

BC549, BC636, BC639, 2N2222 TO-92, 2N2222 TO-18, 2N2369, 2N3055, 2N3904, 2N3906, 2SC5200

How to Safely Long Run BC548 in Circuit

To increase the durability and performance of this device the user much follow the guide lines and should not increase the values as described below. Do not drive the transistor above 30V, always make sure to place its pins right in the circuit, do not provide load more than 500mA, and always use a suitable resistor at the base of the transistor to provide it required current. Do not use or store the device in temperature above +150 centigrade and below -55 centigrade.

Where to Use BC548

BC548 transistor can be used in many general purpose applications; you can use it in the replacement of other general purpose transistor 2N3904, BC547 etc. as described above. A part from that it can be used as a switch to drive load under 500mA. The 500mA collector current is quite good feature for this size and type of transistor therefore you can drive wide variety of loads at the same time in an electronic circuit. Moreover this transistor also has a very good DC current gain and collector dissipation characteristics which makes it ideal to use it in amplification and pre-amplification stages of an electronic circuit.

Component Datasheet

BC548 Datasheet


  • What is BC548 Transistor?

BC548 is a NPN transistor so the collector and emitter will be left open (Reverse biased) when the base pin is held at ground and will be closed (Forward biased) when a signal is provided to base pin. BC548 has a gain value of 110 to 800, this value determines the amplification capacity of the transistor.

  • What is the Use of BC548 Transistor?

BC458 is a general-purpose NPN transistor used in many electronics projects and devices. BC548 transistor is used for amplifying and switching purposes in electrical circuits. Like every other NPN transistor, it consists of three pins: the collector, base, and emitter.

  • How a Transistor Works as a Switch?

By turning a small input current into a large output current, the transistor acts like an amplifier. But it also acts like a switch at the same time. When there is no current to the base, little or no current flows between the collector and the emitter. ... So the base current switches the whole transistor on and off.

  • What is the Difference Between BC547 And BC548?

This group of NPN transistors share many specifications and characteristic curves, but differ in voltage ratings - the BC546 and BC547 are essentially the same as the BC548 but selected with higher breakdown voltages, while the BC549 is a low noise version, and the BC550 is both high-voltage and low-noise.

Ordering & Quality

Photo Mfr. Part # Company Description Package PDF Qty Pricing
BC548 BC548 Company:ON Semiconductor Remark:Bipolar (BJT) Transistor NPN 30V 100mA 300MHz 500mW Through Hole TO-92-3 Package:TO-226-3, TO-92-3 (TO-226AA)
In Stock:On Order

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