BC817 NPN Transistor (SMD)

BC817 Pinout Configuration

Pin Number	Pin Name	Description
1	Base	Controls the biasing of the transistor
2	Emitter	Electrons emitted from the emitter into the first PN junction
3	Collector	Electrons Emitted from Emitter Collected by the Collector

 

Features & Specifications

• Bi-Polar NPN Transistor
• Continuous Collector current (IC) is 500mA
• Emitter Base Voltage (VBE) is 5V
• Base Current(IB) is 50mA maximum
• Available in SOT-323/SC70 Package
• Maximum Collector-Base Voltage |Vcb|: 50 V
• Power Dissipation: 0.46 W
• Transition Frequency:100 MHz
• Noise Figure – 2 dB
• Operating and Storage Junction Temperature Range -65 to +175 °C
• Collector Capacitance 5pF
• DC Current Gain (hFE) is 600 maximum

 

BC817 Equivalent

BC547, BC548, BC549, 2n3904, BC107, 2N2222, 2N3053, 2N2907, BC177B

 

Note: More technical specifications about BC817 transistor can be found in the BC817 datasheet attached at the end of this page.

 

Basic Working of a Transistor

The BC817 Transistor is a general-purpose N-P-N transistor; A junction transistor is simply a sandwiched construction between two layers of N-type material or P-type material. Depending upon the construction transistors are divided into two categories NPN transistor and PNP transistor the, which are shown below, transistors are made up of silicon or germanium, depending upon the application it is chosen.

 

General Description of BC817 Transistor

BC817 is a generic semiconductor device that can be used to amplify or switch signal or power. The BC817 is a NPN Transistor, hence we need to provide a small amount of positive voltage to the base of the transistor through a current limiting resistor generally called RB(Base Resistor) when the required amount of current flows through the base of the transistor, the transistor will turn on. To use this transistor as an amplifier you need to get the gain value from the datasheet of the device, the gain value can differ depending upon the manufacturer, so it's highly recommended to check out the datasheet of the specific device before you do the calculation. The maximum collector current of this transistor is rated at 500mA with a maximum emitter base voltage of 45V. This transistor has a collector emitter voltage of 45V and a collector base voltage of 5V. This transistor can operate with 150*C. Before choosing this transistor, please note that this transistor can provide quite a bit of power compared to its size, so proper thermals are necessary.

 

When this transistor is in biased condition, then it can allow a maximum current of 500mA with a max power of 0.46W across CE(Collector Emitter) Junction, this state of the transistor is called the saturation state and driving a load that consumes more current than 500mA may damage the device in this condition. As you already may know a transistor is a current controlled device so when base current is removed the transistor becomes fully off, in this stage the transistor is working in its Cut-off Region and the Base Emitter voltage could be around 500 mV.

 

How to use BC817 Transistor

Unlike MOSFET’s transistors are current controlled devices, meaning they can be turned on or off by supplying required base current, for the BC817 transistor it is 100mA for 500mA collector current the below graph shows exactly that.

BC817 is a NPN transistor that means it will be left open when no current is applied to its base, but when we apply a base voltage with a current limiting resistor a small amount of base current will flow through the base of the transistor and it will turn on. The simulated circuit below shows how this transistor behaves when a base current is applied to the base and when no current is provided to the base.

When we turn on the transistor by supplying a required current to the base of the transistor it will remain on unless the voltage at the base of the transistor reaches zero. The base of the transistor cannot be left floating otherwise there could be false triggering to the transistor which may lead to issues in the circuit. To resolve the issue, we need to add pulldown resistors. For example, a 10K resistor is used to pull down the base of the transistor.

 

Applications

BC817 Transistor is a very versatile device, its high frequency range, large bandwidth makes it suitable for many different applications.

• LED dimmers or flashers
• Switching Applications
• Preamplifier for Power Amplifier
• High frequency switching
• Modulator and Demodulator for RF frequency

 

2D Model and Dimensions

If you are designing some projects that require the measurement of the component hear is a quick look at the dimension of the device, more info can be found in the datasheet of the device linked down below.