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The KSP2222A NPN transistor is a reliable component widely used in electronic switching, amplification, and general-purpose low-power applications. This article provides a detailed overview of the KSP2222A, including its specifications, pin configuration, working principles, equivalents, applications, and more.
The KSP2222A from onsemi is a versatile NPN transistor designed for general-purpose switching and amplification. With a 40 V collector-emitter rating and up to 600 mA collector current, it reliably handles small motors, relays, and signal-level tasks. Its TO-92 package makes it easy to use in breadboards or through-hole PCB designs, while its high transition frequency (around 300 MHz) supports fast-signal applications.
Engineered for everyday circuits, the KSP2222A delivers stable gain, efficient switching performance, and broad compatibility with common alternatives such as the 2N2222A - just verify the pinout when substituting. Its modest power dissipation of 625 mW means it’s best suited for low-to-medium power tasks, where it provides excellent reliability without excessive heat.
If you are interested in purchasing the KSP2222A, feel free to contact us for pricing and availability.
| Pin Number | Pin Name | Description |
| 1 | Emitter | Current flows out; typically connected to ground in NPN circuits. |
| 2 | Base | Controls the transistor's switching/amplification. |
| 3 | Collector | Main current path; connects to the load in switching applications. |
| Transistor | Type | Category | VCEO (Max Voltage) | IC (Max Current) | Package | Notes |
| 2N2222A | NPN | Equivalent | 40 V | 0.6 A | TO-92 / TO-18 | Direct equivalent; same class and behavior |
| 2N3904 | NPN | Alternative | 40 V | 0.2 A | TO-92 | Lower current; good for small-signal circuits |
| 2N2369 | NPN | Alternative | 40 V | 0.2 A | TO-18 / TO-92 | High-speed switching; lower current |
| BC547 | NPN | Alternative | 45 V | 0.1 A | TO-92 | Lower current; general-purpose |
| BC549 | NPN | Alternative | 30 V | 0.1 A | TO-92 | Low-noise; lower voltage |
| BC639 | NPN | Alternative (Higher-spec) | 80 V | 1.0 A | TO-92 | Higher voltage & current; usable if needed |
| Parameter | Value |
| Transistor Type | NPN BJT |
| Package | TO-92 |
| VCEO (Collector–Emitter Voltage) | 40 V |
| VCBO (Collector–Base Voltage) | 75 V |
| VEBO (Emitter–Base Voltage) | 6 V |
| IC (Continuous Collector Current) | 600 mA |
| Power Dissipation (Pᵈ) | 625 mW |
| hFE (DC Gain) | 35–300 |
| Transition Frequency (fT) | ~300 MHz |
| Collector–Emitter Saturation Voltage (VCE(sat)) | 0.3–1.0 V |
| Pinout | 1-Emitter, 2-Base, 3-Collector |
The first diagrams illustrate how the transistor functions in two common applications: amplification and switching. In the amplifier circuit, the KSP2222A operates in its active region, where small input signals applied to the base are boosted into larger output signals at the collector. Components such as resistors R3–R6 and capacitors C1–C2 set the biasing and stabilize the signal, ensuring linear amplification. This configuration is typical for audio or sensor-signal amplification where the transistor continuously adjusts its collector current in response to input variations.
In the switching circuit, the KSP2222A is used as an on/off electronic switch. A control voltage applied to the base through resistor R1 determines whether current flows through the collector to power a load such as a motor. When the base receives sufficient drive current, the transistor enters saturation, allowing maximum current to pass; when the base voltage is removed, it fully switches off. This simple and efficient setup makes the KSP2222A ideal for digital control, microcontroller interfaces, or low-power motor and relay driving application.
-General-purpose signal amplification in audio, sensor, and analog circuits
-Low-power switching for motors, relays, LEDs, and small loads
-Microcontroller interface circuits for driving external devices
-High-frequency applications due to its ~300 MHz transition frequency
-Pulse, digital, and square-wave switching circuits
-Small-signal RF circuits and fast-switching applications
-Inverter and oscillator circuits
-Current regulation and biasing stages in electronic systems
-Hobby electronics, prototyping, and educational circuits
-Replacement for common NPN types like 2N2222A in many general applications
| Specification | KSP2222A | 2N2222A | BC547 |
| Transistor Type | NPN | NPN | NPN |
| Package | TO-92 | TO-92 / TO-18 | TO-92 |
| VCEO (Max Voltage) | 40 V | 40 V | 45 V |
| IC (Max Collector Current) | 600 mA | 600 mA | 100 mA |
| Power Dissipation | ~625 mW | ~500–625 mW | ~500 mW |
| Transition Frequency (fT) | ~300 MHz | ~250–300 MHz | ~300 MHz |
| Gain (hFE) | 35–300 | 35–300 | 110–800 (varies by grade) |
| Usage Category | General purpose | General purpose | Low-noise, low-current |
| Suitable For | Switching, small loads, amplification | Same as KSP2222A | Low-current signal amplification |
| Closest Equivalent | 2N2222A | KSP2222A | BC547 family only |
-Supports relatively high current (up to 600 mA) for a TO-92 NPN transistor
-Widely available and inexpensive, making it ideal for general-purpose use
-High transition frequency (~300 MHz) suitable for fast switching and some RF applications
-Works well as both an amplifier and a switch
-Compatible with many common circuits using 2N2222A-type transistors
-Easy to use in breadboards and through-hole PCB designs
-Good gain range (hFE) for signal-level applications
-TO-92 package limits power dissipation (around 625 mW)
-Not suitable for high-power or high-current loads beyond its 600 mA rating
-Gain (hFE) varies significantly with current and temperature
-Requires proper heat management at higher loads
-Not designed for precision or low-noise applications compared to specialized transistors
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