BC549 transistor: This is an NPN transistor so the collector and emitter will be on when supplying a small current to the base. BC549 is a low current transistor so the max amount of current that could flow through the Collector pin (Ic) is 100mA, so we cannot connect loads that use above 100mA and load voltage above 30 volts using this transistor. BC549 has a reasonable gain value (HEF) from 420 to 800; this value controls the amplification capacity of the transistor.

When the transistor is fully biassed then it can permit a max of 100mA to flow across the collector and emitter This step is called Saturation Region. When the base current is removed the transistor will be fully off, this step is called  Cut-off Region. The pin configuration of BC549.

 BC549 pinout chart and Diagram

Pin No. Pin Name Description
1 Emitter Current Drains in through emitter.
2 Base Controls the current between the collector and Emitter.
3 Collector Current flows out through collectors.

Features of BC549 Transistor:

  • Type of Package: TO-92
  • Type of Transistor: NPN
  • Maximum Collector Current(IC): 100mA
  • Max Collector & Emitter Voltage (VCE): 30V
  • Maximum Collector-Base Voltage (VCB): 30volt
  • Max Emitter-Base Voltage (VEBO): 5volt
  • Maximum Collector Dissipation (Pc):  500mW
  • Maximum Transition Frequency (fT): 150 MHz
  • Minimum & Max DC Current Gain (hFE): 110 to 800
  • Maximum Storage and Operating temperature Should Be: -65 to +150 Centigrade

 The complement of the bc549 Transistor

The Complement of this transistor is: BC557, BC558, BC559

BC549 equivalent

Bc549 transistor substitute, alternate and equivalent are:BC548, 2N2222, 2N3904, BC550, C945, PN100, BC337


There is a list of SMD alternates of To-92

  • BC546 NPN (TO-92) BC846 NPN (SOT-23)
  • BC547 NPN (TO-92) BC847 NPN (SOT-23)
  • BC548 NPN (TO-92) BC848 NPN (SOT-23)
  • BC549 NPN (TO-92) BC849 NPN(SOT-23)
  • BC556 PNP (TO-92) BC856 PNP (SOT-23)
  • BC557 PNP (TO-92) BC857 PNP (SOT-23)
  • BC558 PNP (TO-92) BC858 PNP (SOT-23)
  • BC559 PNP (TO-92) BC859 PNP (SOT-23)

Bc549 transistor working

The working of the 549 is the same as the NPN transistor. When a small amount of current on the base has been applied the emitter and collector start to flow the high level of current. It is an NPN transistor that is way + current is applied on the base of the transistor. When the base is connected to the ground the transistor remains in a fully cut-off stage.

How We Can Use BC549:

BC549 transistor can also be used in many general-purpose applications, for example, it can be used in the audio preamplifier, audio amplifier, and circuits, this transistor can also be used for signal amplification purposes due to its high gain characteristic, the emitter-base voltage is only 5V  which BC549 can be used at the output of the microcontrollers, with the 100mA collector current NPN transistor can be used to control a variety of loads in the electronic circuit like power transistors, relays, MOSFETs, LEDs,  etc.

Applications of NPN transistor

  • Darlington pair
  • Switching small loads
  • Audio Noise filters
  • The LED array sequence controller
  • Small signal amplifiers

BC549 vs BC547 Transistor

BC547 and bc549 both are NPN and both are alternate of each other with little difference. The difference between these two are
BC549 datasheet