Bipolar Transistors

A bipolar transistor is a type of semiconductor and uses two charge carriers instead of one. Usually used in circuits, its function is to either augment a current or to behave as a switch. Acting as either an insulator or a conductor means the transistor can change easily between a switch or an amplifier.

Also known as bipolar junction transistors, each one is made from three silicon layers and is a three-pin active device . Although silicon is known to be a poor conductor, when treated in a certain way with a chemical process, its ability to conduct electricity improves. This is also known as 'doping'.

How do bipolar transistors work ?

Standard bipolar transistor characteristics include two PN (positive-negative) junctions and three connecting bipolar transistor terminals: the emitter, the collector and the base. The bipolar transistor controls the electrical current from the emitter to the collector and regulates it, depending on the voltage applied to the base.

When a small current is injected at the base, a larger current can be controlled through the emitter and collector terminals. This makes the device great for either amplification or switching functions.

Advantages of using a bipolar transistor junction include:

• The ability to use it in either high or low frequency applications
• A large gain bandwidth
• A better voltage gain
• Solid performance at high frequencies

For these reasons, a bipolar transistor amplifier circuit is often used in electronic audio or wireless transmitters.

Bipolar transistors Active mode is the most common use, meaning the transistor can act as an amplifier, increasing the electrical current from the collector to the emitter.

In saturation mode, the current is allowed to flow freely between the collector and the emitter. This is also known as 'on' mode. The cut-off mode is the opposite of saturation and means there is no current flowing to create an output. These 'on/off' modes mean the bipolar transistor functions extremely effectively as a switch.

Types of bipolar transistors

There are two main types of bipolar transistors: the PNP bipolar transistor or the NPN bipolar transistor. The most common transistor configuration is the NPN bipolar power transistor where the current flows from the collector to the emitter. In the PNP configuration, this is reversed and the current flows from the emitter to the collector.

A PNP bipolar transistor is turned on with a low signal, whereas an NPN bipolar transistor uses a high signal. However, there is also a dual NPN PNP complementary bipolar transistor which is a six-pin hybrid device containing both.

Another type of bipolar transistor is an insulated gate bipolar transistor. Comprising four layers in the arrangement PNPN, these transistors are becoming increasingly common in modern applications such as smart homes, the power supply for airport security scanners as well as in electric vehicle chargers .

Specifications

Our bipolar junction transistors come in a wide range of specifications to suit your needs. Options for your transistor include NPN, PNP plus the dual NPN PNP complementary bipolar transistor. With a large range of collector current and collector to emitter voltage options, including high voltage bipolar transistors up to 1500v, you're sure to find the right product for you.

With a choice of mounting options and number of pins, selecting the perfect bipolar transistor couldn't be easier. Plus, our drop-down menus allow you to easily filter our products to your exact specifications.

Choose the best bipolar transistor for your needs

We stock our products from well-respected manufacturers, including big names such as:

• Diodes Inc.
• NTE Electronics Inc.
• ON Semiconductor
• Panasonic
• Solid State Manufacturing

You can search for your preferred brand using the 'manufacturer' filter, so getting the part you need has never been easier.

Use our Quick Order Portal to search a product by stock or part number and add it to your cart if you already know what you're looking for. Alternatively, if you need any advice or want to ask any questions, contact us for expert help and we'll be happy to talk through your product needs.

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