BC548 NPN Transistor: Datasheet, Equivalent, and Circuit

The BC548 is an NPN bipolar junction transistor that can be used in many general purpose applications. It can handle maximum current of 500mA which is enough to drive many other components such as ICS, other transistors, portion of a circuits, relays, LEDs etc. The max collector dissipation of the BC548 is 625 miliWatt which is another good feature to use it as a small amplifier.

This series comes in four different part numbers: BC548, BC548A, BC548B and BC548C. The only difference between them is their DC current gain value. BC548 current gain value is from 110 to 800, BC548A is from 110 to 220, BC548B is from 200 to 450, and BC548C is from 420 to 800.

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Footprint

3D Model

• Package Type: TO-92

• Transistor Type: NPN

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

• Max Collector-Emitter Voltage (VCE): 30 V

• Max Collector-Base Voltage (VCB): 30 V

• Max Emitter-Base Voltage (VEBO): 5 V

• 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 is an 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. The BC548 has a gain value of 110 to 800 which 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.

ON Semiconductor BC548 technical specifications, attributes, parameters and parts with similar specifications to ON Semiconductor BC548.

The BC548 transistor can be used in many general purpose applications. It can be used in the replacement of other general purpose transistors like 2N3904, BC547 etc. The BC548 can also 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.

• BC548 as Amplifier

A transistor 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:

•  Common emitter amplifier

•  Common collector amplifier

•  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 formula

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

• BC548 as Switch

The regions 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.

BC548 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.

BC548 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.

• Darlington Pairs

• Sensor Circuits

• Audio Preamplifiers

• Audio Amplifier Stages

• Switching Loads under 500mA

• Driver Modules like Relay Driver, LED driver etc

• Sensor circuits

• Amplifier circuits

• Audio preamp circuits

• Touch switch circuits

• RF circuits

• PWM circuits

• Quick switching devices

• Relay driving

• Alarm devices

• LED flash circuits

• Heat sensor circuits

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Download datasheets and manufacturer documentation for ON Semiconductor BC548.