General Purpose and Low VCE(sat) Transistors

Technical Documentation

The portfolio of general-purpose and Low VCE(sat) transistors from onsemi includes varilous combinations of NPN and PNP transition available in dual and individual packages. The portfolio features low to ultra-low saturation voltage (VCE(sat) as low as 0.015 V), along with operational currents and voltages to fit various applications. General-purpose and Low VCE(sat) transistors from onsemi provide ideal performance characteristics through small ON-resistance (Ron), Ultrasmall package to facilitate miniaturization, Small Variance in Storage Time, Built-in Free Wheeling Diode, Excellent Second Breakdown Capability, Improved AOI Capability, High Gain Amplification, High Collector-Base Breakdown Voltage.

The wide variety of transistors in this category are available to cover situations requiring the full-range of low-speed to high-speed switching applications. Applications include ESD Protection, Polarity Reversal Protection, Data Line Protection, Inductive Load Protection, Steering Logic, DC / DC converter, relay drivers, lamp drivers, motor drivers, flash, Low-frequency Amplifier, small motor drive, muting circuit, and High Side Switching. The portfolio also includes AEC-Q101 Qualified and PPAP Capable options specifically engineered and qualified for automotive industry applications.

What Is a Bipolar Junction Transistor (BJT)?

Bipolar junction transistors (BJTs) are a type of active semiconductor device that can control the switching and amplification of current in an electronic circuit. Transistors control voltage and current through three leads, the base, collector, and emitter.

The emitter region is made up mostly of n-doped material and supplies electrons to the base region. The base region is mostly made up of p-doped material and supplies holes to the collector region. Because of this, there is a depletion region between the emitter and base materials where free electrons and free holes cannot exist. This forms the transistor's input signals. The collector junction supplies the majority of carriers with an electrical load.

When a voltage is applied to the forward base via the emitter-base junction, charge carriers can cross over into the base region. There are now two junctions having majority carriers flowing across them. The collector current also has a voltage applied to it so that a more robust current from it can be produced by recombination at both of the two junctions within the transistor. Since there is more current flowing through both junctions, more charge carrier concentrations can recombine at each of these individual junctions, which produces more significant gain. A BJT is complementary to a Field Effect Transistor.

The BJT switch is designed with silicon and a higher bandgap, which helps this transistor function better in low voltage environments. They can be used as voltage dividers. These single transistors are designed to function as current-controlling devices, meaning they help to regulate the amount of base current flowing through a circuit.

What Are the Operating Regions of a BJT?

A bipolar junction transistor (BJT) has three distinct regions: active, cut-off, and saturation. These regions are determined by the current flowing through the base of the BJT. Both the base and collector current are zero in the cut-off region. The BJT is in saturation when both are at their maximum values. When the emitter doping is controlled by the input current and output current, it is in the active region.

What Are the Applications of a BJT?

The applications of a bipolar junction transistor, or BJT, include:

1) They are used in radiofrequency amplifiers and oscillators

The most popular application for BJT transistors is amplification; they are utilized in analog and digital circuits, radios, computers, and almost any other electronic device. Bipolar transistors are so named because they conduct by using both majority and minority charge carriers. This allows them to amplify signals.They are used in radiofrequency amplifiers and oscillators, where their high gain and high output impedance allow more compact circuits than would be possible with a JFET (junction field-effect transistor) at the same frequencies.

2) They are used in high-frequency switch circuits

The bipolar junction transistors, or BJTs, are used in high-frequency switch integrated circuits and high-frequency amplifiers to control the current flows in high-resistance semiconductor junctions. The heterojunction bipolar transistor consists of two PNP or NPN transistors facing each other in a single package. This design allows a larger current to pass through the device as compared to a single common transistor. As a result, BJTs can be used in applications that require high-frequency switches through stack exchange. The device is turned on and off hundreds of thousands of times per second in this capacity.

3) They are used in low-noise preamplifiers and amplifier circuits

Bipolar transistors are used in many electronic devices such as TVs, radios, cell phones, and computers for signal amplification, signal switching, and sign. It is a valuable component for low-noise preamplifiers and differential amplifier circuits.

4) It functions as a vacuum tube triode

It is found in many integrated circuits and lamps, such as light-emitting diodes or LEDs. It only takes a small voltage to turn the element on, producing light when it becomes electrically conductive.

5) They are used in clipping circuits and waveshaping

A Bipolar Junction Transistor (BJT) can be used in clipping circuits and wave shaping because of its unique output characteristics. This is done when two diodes are connected between the collector and emitter.

6) They are used in timer and time delay circuits

When used as a simple switch, a standard transistor can keep a circuit turned on for a specific duration of time. When the switch is turned on, the current flowing through it charges up the capacitor. When the switch is turned off, the capacitor discharges, keeping the circuit active for a specific amount of time before shutting off. Another use for transistors in timers and time delay digital or analog circuits is to control pulse repetition frequency as part of circuit elements such as timers/counters and oscillators.

Contact our team at onsemi to learn more.

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