Onsemi MPS2222AG NPN Bipolar Junction Transistor: Datasheet, Pinout, and Application Circuits
The MPS2222AG from Onsemi is a widely used and versatile NPN bipolar junction transistor (BJT) renowned for its general-purpose amplification and switching capabilities. This article provides a detailed overview of its key specifications, pin configuration, and common circuit implementations.
Datasheet Overview and Key Specifications
The MPS2222AG is the Onsemi equivalent of the legendary 2N2222A transistor. It is designed for medium-power applications and is characterized by its high current gain and fast switching speeds. Key absolute maximum ratings and electrical characteristics from its datasheet include:
Collector-Emitter Voltage (VCE): 40 V
Collector Current (IC): 800 mA (Continuous)
DC Current Gain (hFE): 100 @ 150 mA, 10 V (Typical, can range from 50 to 300)
Power Dissipation (PD): 625 mW
Transition Frequency (fT): 300 MHz (Typical)
Collector-Emitter Saturation Voltage (VCE(sat)): < 0.4 V @ 150 mA (Typical)
These specifications make it an excellent choice for a broad array of applications, including switching inductive loads like relays and motors, driving LEDs, and as a small-signal amplifier in audio and RF stages.
Pinout Configuration
The pinout of the MPS2222AG is crucial for correct circuit design. The transistor is commonly available in the TO-92 package. When viewing the flat side of the package with the pins facing downward, the pin assignment is as follows:
Pin 1 (Left): Emitter (E)
Pin 2 (Middle): Base (B)
Pin 3 (Right): Collector (C)
It is critical to confirm this configuration with a multimeter or the datasheet before installation, as incorrect wiring can instantly destroy the component.
Application Circuits
1. Low-Side Switch Circuit
The most common use of the MPS2222AG is as a low-side switch to control higher-power devices like motors, solenoids, or LEDs from a microcontroller (e.g., an Arduino) or logic circuit.
How it works: A small current applied to the base (via a current-limiting resistor, RB) allows a much larger current to flow from the collector to the emitter, turning on the load connected to VCC. A flyback diode (D1) is essential when switching inductive loads to protect the transistor from voltage spikes generated when the load is turned off.
Component Sizing:
Base Resistor (RB): Calculated to provide sufficient base current (IB) to saturate the transistor. A typical value is between 1kΩ to 10kΩ.
RB ≈ (VIN - VBE) / (IC / hFE)
Flyback Diode (D1): A general-purpose diode like 1N4148 or 1N4007.
2. Common-Emitter Amplifier
The MPS2222AG can be configured as a simple analog amplifier to amplify small AC signals, such as from a microphone.
How it works: The circuit is biased using resistors R1 and R2 to set the operating point (Q-point) in the active region. The input signal is coupled through capacitor C1 and modulates the base current, causing a larger, amplified analog signal at the collector output, which is then coupled through capacitor C2. The emitter resistor (RE) provides stability against temperature variations.
ICGOODFIND: The Onsemi MPS2222AG stands as a fundamental building block in electronics, prized for its robust performance, high reliability, and cost-effectiveness. Its ability to handle moderate currents and switch quickly makes it an indispensable component for hobbyists and engineers alike, serving as the workhorse for countless switching and amplification tasks across consumer, industrial, and automotive applications.
Keywords: NPN BJT, Switching Transistor, Low-Side Switch, Common-Emitter Amplifier, Saturation Voltage
