Infineon SMBTA56 PNP Silicon Epitaxial Transistor: Datasheet, Pinout, and Application Circuit Guide
The Infineon SMBTA56 is a general-purpose PNP bipolar junction transistor (BJT) housed in a compact SOT-23 surface-mount package. Designed for high-voltage applications, this silicon epitaxial transistor is a robust solution for switching and amplification in a wide range of electronic circuits, from power management to signal inversion.
Datasheet Overview: Key Specifications
The SMBTA56 is characterized by its ability to operate at relatively high voltages and currents for its small size. Key absolute maximum ratings and electrical characteristics from its datasheet include:
Collector-Emitter Voltage (VCE): -80 V – This high voltage rating makes it suitable for off-line power supplies, electronic ballasts, and other high-voltage circuits.
Collector Current (IC): -500 mA (Continuous) – A sufficient current rating for driving relays, LEDs, and small motors.
Total Power Dissipation (Ptot): 500 mW – The maximum power the device can dissipate, which is limited by its small package.
DC Current Gain (hFE): Ranges from 40 to 250, typically around 100, depending on the collector current (IC) and collector-emitter voltage (VCE).
Transition Frequency (fT): 100 MHz (typical) – This indicates its useful frequency range for amplification applications.
Pinout Configuration
The SMBTA56 comes in the industry-standard SOT-23 package. When viewing the component with the flat side facing you and the pins pointing downward, the pin configuration is as follows:
Pin 1 (Left): Emitter (E)
Pin 2 (Middle): Base (B)
Pin 3 (Right): Collector (C)
It is crucial to confirm this pinout with a multimeter or the manufacturer's datasheet before soldering, as pinouts can occasionally vary between manufacturers for the same package type.
Application Circuit Guide
A common use for the SMBTA56 is as a low-side switch. In this configuration, the transistor is placed between the load and ground, allowing a small current from a microcontroller (e.g., an Arduino or ESP32) to control a much larger load current.
Basic Low-Side Switch Circuit:
1. Load: Connect one terminal of your load (e.g., a relay coil, a motor, or a string of LEDs) to the positive supply voltage (VCC).
2. Transistor: Connect the other terminal of the load to the Collector of the SMBTA56.
3. Ground: Connect the Emitter of the transistor directly to ground.
4. Base Resistor (Critical Component): Connect a current-limiting resistor (typically between 1kΩ to 10kΩ) from the Base of the transistor to the control signal output (e.g., a GPIO pin of a microcontroller). This resistor protects both the control source and the transistor base by limiting the base current (IB).
5. Flyback Diode: If the load is inductive (like a relay or motor coil), a flyback diode (e.g., 1N4148) must be connected in reverse bias across the load (anode to collector, cathode to VCC) to suppress voltage spikes that could destroy the transistor.
How it Works: To turn the load ON, the control signal output is set to a LOW (0V) state. This creates a current path from VCC through the load and the base resistor into the base, saturating the PNP transistor and allowing current to flow from the emitter to the collector to ground. To turn the load OFF, the control signal is set to a HIGH (e.g., 3.3V or 5V) state, which stops the base current and cuts off the transistor.
ICGOODFIND: The Infineon SMBTA56 is an excellent choice for designers seeking a high-voltage, compact PNP switching transistor. Its SOT-23 package offers a small footprint for space-constrained PCBs, while its robust electrical characteristics provide reliability in demanding applications like power supply inverters, motor control interfaces, and as a complement to NPN transistors in push-pull output stages.
Keywords: PNP Transistor, SOT-23, High Voltage Switching, Low-Side Switch, BJT
