Infineon SMBT3904E6327HTSA1 NPN Switching Transistor: Datasheet, Pinout, and Application Circuits

The Infineon SMBT3904E6327HTSA1 is a high-performance NPN bipolar junction transistor (BJT) designed primarily for high-speed switching and amplification applications. Encapsulated in a space-saving SOT-23 surface-mount package, this component is a robust and reliable choice for modern electronic designs, from industrial control systems to consumer electronics.

Datasheet Overview and Key Specifications

The transistor's datasheet provides critical parameters that define its operational limits and performance. Key absolute maximum ratings include a collector-emitter voltage (V_CE) of 40 V and a continuous collector current (I_C) of 200 mA. For switching applications, its dynamic characteristics are paramount. The device boasts an excellent transition frequency (f_T) of 300 MHz, ensuring fast switching speeds. Furthermore, it features very low turn-on and turn-off times (t_d, t_r, t_s, t_f), typically in the tens of nanoseconds, which minimizes switching losses. The DC current gain (h_FE) is typically 100 at 10 mA, providing good amplification.

Pinout Configuration

The SMBT3904E6327HTSA1 comes in a standard SOT-23 package with three pins. When viewing the flat side of the component with the pins facing downward, the pinout is as follows:

Pin 1 (Left): Emitter (E)

Pin 2 (Middle): Base (B)

Pin 3 (Right): Collector (C)

Correct identification of these pins is critical for proper circuit operation and to prevent damage to the device during soldering and testing.

Application Circuits

This transistor's primary function is as a switch or an amplifier. Below are two fundamental circuit configurations.

1. Low-Side Switch Circuit

This is one of the most common applications for driving loads like relays, LEDs, or motors. The load is placed between the positive supply rail (V_CC) and the transistor's collector. The emitter is connected directly to ground. A current-limiting resistor is placed in series with the base, and a digital signal from a microcontroller or logic IC (e.g., 3.3V or 5V) is applied to turn the transistor ON (saturated) or OFF. When the base receives sufficient current, the transistor saturates, acting as a closed switch and allowing current to flow through the load to ground.

2. Common-Emitter Amplifier

In this classic amplifier configuration, a small AC signal (e.g., from a microphone) is coupled to the base through a capacitor. The output, an inverted and amplified version of the input signal, is taken from the collector. Resistors are used to bias the transistor into its linear operating region (R1, R2), set the voltage gain (R_C), and provide thermal stability (R_E). The high f_T of the SMBT3904 makes it suitable for amplifying signals well into the RF range.

ICGOODFIND

The Infineon SMBT3904E6327HTSA1 stands out as an exceptionally versatile and high-performance NPN switching transistor. Its optimal balance of speed, current handling, and voltage capability makes it an ideal, industry-standard choice for designers. Whether the task is interfacing low-power logic with higher-current peripherals or constructing a high-frequency amplifier, this component delivers reliable performance in a compact, surface-mount package, solidifying its role as a fundamental building block in countless electronic applications.

Keywords: NPN Transistor, Switching Application, SOT-23 Package, High-Speed Switching, Common-Emitter Amplifier.