Basics of BC547 Transistor Pinout, Specs and Uses

Q: Is BC547 an NPN or PNP transistor?

It is an NPN bipolar junction transistor.

Q: What is the maximum current of a BC547 transistor?

The maximum collector current of a BC547 transistor is 100mA

Q: What is the principle of BC547?

The transistor operates on the principle of bipolar junction transistor (BJT) action, where a small current at the base controls a larger current flow between the collector and emitter terminals. It is an NPN transistor commonly used for amplification and switching applications in electronic circuits.

Last updated on March 26th, 2024 at 06:12 pm

BC547 is an NPN bipolar junction transistor used in electronic circuits for amplification and switching. It belongs to a popular ” BC” family of transistors, including BC548, BC549, etc.

The BC547 transistor typically comes in two packages: SMD and TO-92. It exhibits a Minimum and Maximum DC Current Gain (hFE) ranging from 110 to 800. The transistor has a maximum collector current of 100mA and a maximum collector-emitter voltage of 45V, with a collector-to-base voltage of 50V. Additionally, the transition frequency of the transistor is 300MHz.

The transistor acts as a switch between the collector and emitter. If the base of the transistor is given enough current, this switch closes, and the current flows from the collector to the emitter.

So a small current to the base pin of the transistor switches the large current between the collector and the emitter.

BC547 is also used for the amplification of the input signals. A small amount of current at the base is used to control a large amount of current between the collector and emitter.

BC547 pinout

This transistor has three pins, starting from left: collector, emitter, and base respectively.

Pin Number	Pin Name	Description
1	Collector	This pin act as an inlet as the current enters the transistor from here. The collector is denoted by ‘C’.
2	Base	This pin controls the transistor biasing. The base is denoted by ‘B’.
3	Emitter	This pin act as an outlet and the current comes out of the transistor from here. The emitter is denoted by ‘ E’.

Technical specifications

Some of the important specifications of this transistor are listed below:

Package-Type: TO-92
Transistor Type: NPN
Max Collector Current (I_C): 100mA
Max Collector-Emitter Voltage (V_CE): 45V
Max Collector-Base Voltage (V_CB): 50V
Max Emitter-Base Voltage (VEBO): 6V
Max Collector Dissipation (Pc): 500 milliwatt
Max Transition Frequency (fT): 300 MHz
Minimum & Maximum DC Current Gain (h_FE): 110 – 800
Max Storage & Operating temperature Should Be: -65 to +150 Centigrade
Low Noise: 2-10 dB

Uses and applications

BC547 is used commonly in:

The highest transition frequency is 300MHz of this transistor. Thus, it can also be used in RF circuits.
Amplification of current
Audio Amplifiers
Switching Loads < 100mA
Transistor Darlington Pairs
Amplifiers like Audio, signal, etc.
Darlington pair
Quick switching
PWM (Pulse Width Modulation)

BC547 transistor as a switch

The regions responsible for a transistor to work as a switch are the Saturation Region and the Cut-off Region. When we apply 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.

To use the transistor as a switch, it must be driven into the saturation region with enough base current. A transistor operates as a closed switch under the saturation region.

As soon as a positive signal (in the 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.

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.

BC547 as an amplifier

A transistor acts as an amplifier by increasing the strength of a weak signal applied at its base. Transistors work as an amplifier in the active region or linear region. The figure given below shows how to use a transistor as an emitter amplifier.

**Image Source: instrumentationtools

In this region, with the increase in the base current, the collector current also increases proportionally according to the formula:

I_C=β I_B

Here, I_C = collector current

Β = current amplification factor

I_B = base current

Thus, a small input signal results in a large output, which implies that the transistor works as an amplifier.

BC547 transistor equivalent

BC547 transistor can be used as an alternative to many transistors:

BC548, BC549, BC636, BC639, 2N2222 TO-92, 2N2222 TO-18, 2N2369, 2N3055 and 2N3904 all are BC547 transistor equivalent.

Datasheet

It comes in two packages- SMD package and the TO-92 package.

Click this link to view the entire DATASHEET

You can find detailed information on the datasheet given above. Specifications and characteristics like Absolute maximum ratings, Block diagrams, biasing methods, and package dimensions can be found in the datasheet.

BC547 TO-92 package dimensions

BC547 transistor projects

You can make many good beginner-level projects using this transistor. Some of the beginner projects are listed below:

Not Gate using a Transistor on Breadboard

NOR Gate using a Transistor on Breadboard

Rain Sensor Alarm using two BC547 Transistor

Where to buy?

You can easily find this transistor in your local electronics store. For online purchases, we recommend this best deal on Amazon:

FAQs

Is BC547 an NPN or PNP transistor?