Infineon SMBTA92 PNP High-Voltage Transistor: Datasheet, Pinout, and Application Circuits
The Infineon SMBTA92 is a small-signal PNP transistor housed in a compact SOT-23 surface-mount package, specifically engineered for high-voltage applications. This device is a popular choice for designers who require robust switching and amplification in circuits where high voltages are present, all within a minimal PCB footprint.
This article provides a detailed overview of the SMBTA92, covering its key specifications, pinout configuration, and typical application circuits.
Datasheet Overview and Key Specifications
The SMBTA92 is characterized by its ability to handle high voltages between its emitter and collector terminals. Its primary electrical characteristics make it suitable for a variety of electronic functions.
The most critical parameters from its datasheet include:
Collector-Emitter Voltage (VCEO): -300 V. This is the transistor's standout feature, defining its maximum voltage capability in the off state.
Collector Current (IC): -500 mA (continuous). This specifies the maximum continuous current it can switch through its collector.
Power Dissipation (Ptot): 330 mW. The maximum power the device can dissipate without exceeding its junction temperature limit.
DC Current Gain (hFE): Ranges typically from 25 to 250, depending on the collector current and specific batch, indicating its amplification factor.
Transition Frequency (fT): 50 MHz. This indicates the frequency at which the transistor's current gain drops to unity, defining its usefulness in amplification applications.
These parameters make the SMBTA92 ideal for use as a high-voltage switch, in offline power supplies, for level shifting, and as a driver for other higher-power devices.
Pinout Configuration
Correctly identifying the pinout is crucial for circuit design and PCB layout. The SMBTA92 comes in the SOT-23 package. When viewing the component with the flat side facing you and the pins pointing downward, the pin assignment is as follows:
Pin 1 (Emitter): This is the input for the majority charge carriers in a PNP transistor.
Pin 2 (Base): The control terminal. A negative current relative to the emitter is applied here to turn the transistor on.
Pin 3 (Collector): The output terminal, which connects to the load.
Warning: Always consult the manufacturer's datasheet for the specific package drawing, as pinouts can sometimes vary between manufacturers, though the SMBTA92 is standardized.
Application Circuits
The SMBTA92 excels in two primary roles: as a switch and as an amplifier.
1. High-Voltage Switching Circuit
A common use is to drive a relay, lamp, or LED strip from a low-voltage microcontroller (e.g., a 3.3V or 5V GPIO pin). In this configuration, the transistor acts as an inverting switch.
The load (e.g., a relay coil) is connected between the high-voltage supply (e.g., +24V or +100V) and the collector pin.
The emitter is connected directly to the positive high-voltage supply rail.
A base resistor (e.g., 1kΩ to 10kΩ) is essential to limit the base current. It connects the microcontroller's GPIO pin to the base of the transistor.
To ensure reliable turn-off, a pull-up resistor is sometimes added between the base and emitter.
When the GPIO output is LOW (0V), it creates a negative voltage at the base relative to the emitter, turning the PNP transistor ON and allowing current to flow through the load. When the GPIO is HIGH (3.3V), the base-emitter junction is not forward-biased, and the transistor turns OFF.
2. Simple High-Voltage Amplifier
The SMBTA92 can also be configured in a common-emitter amplifier topology to amplify small AC signals. This circuit requires careful biasing of the base with a voltage divider network to set the operating point (Q-point) in the active region. The high VCEO allows the amplified output signal to swing over a very wide voltage range, which is useful in specific industrial and diagnostic equipment.
ICGOODFIND Summary
The Infineon SMBTA92 is a highly reliable and efficient PNP transistor that provides an excellent solution for managing high-voltage circuits in a space-constrained SMT design. Its ability to switch up to -300V and -500mA makes it exceptionally versatile for power supply interfaces, driver stages, and amplification tasks where voltage levels exceed the capabilities of standard small-signal transistors. Engineers consistently choose it for its robust performance and the design flexibility offered by its miniature SOT-23 package.
Keywords:
1. High-Voltage Switching
2. PNP Transistor
3. SOT-23 Package
4. Application Circuits
5. Datasheet Specifications
