Infineon BSS123NH6327 N-Channel Logic Level Enhancement Mode MOSFET: Datasheet, Pinout, and Application Circuits
The Infineon BSS123NH6327 is a popular N-Channel Logic Level Enhancement Mode MOSFET designed for low-voltage, low-power switching applications. Its ability to be driven directly from logic circuits (like 3.3V or 5V microcontrollers) makes it a fundamental component in modern electronics, from consumer gadgets to industrial automation systems.
This surface-mount device, supplied in the compact SOT-23 (TO-236AB) package, is renowned for its fast switching speeds and low on-state resistance (RDS(on)), which contribute to high efficiency and minimal power loss in circuits.
Datasheet Overview: Key Parameters
A thorough review of the datasheet reveals the critical specifications that define the BSS123NH6327's performance:
Drain-Source Voltage (VDS): 100 V. This maximum voltage rating makes it suitable for a wide range of low-power offline and DC-DC applications.
Continuous Drain Current (ID): 170 mA at a case temperature of 25°C. This defines its current-carrying capability for load switching.
On-State Resistance (RDS(on)): A maximum of 6 Ω at VGS = 10 V, ID = 50 mA. Crucially, it is specified down to 3.5 Ω at VGS = 4.5 V, ensuring effective operation with 5V logic, and 5 Ω at VGS = 3 V, making it compatible with 3.3V systems.
Gate Threshold Voltage (VGS(th)): Between 0.8 V and 2.2 V. This low threshold is what qualifies it as a "logic-level" MOSFET, meaning it can be fully turned on by typical microcontroller GPIO pins.
Fast Switching Characteristics: The device features low gate charge and capacitances, enabling high-speed switching which is essential for PWM control and other digital applications.
Pinout Configuration
The BSS123NH6327 in the SOT-23 package has three pins:
1. Gate (G): This is the control pin. Applying a voltage above the threshold voltage (relative to the Source) turns the MOSFET ON.
2. Drain (D): This is the output pin connected to the load. When the MOSFET is ON, current flows from the Drain to the Source.
3. Source (S): This is the common or ground reference pin for the Gate control signal and the load current return path.
Application Circuits
The primary use of the BSS123NH6327 is as a low-side switch. This configuration is simple and highly effective for controlling loads such as LEDs, relays, solenoids, and motors.
1. Basic Low-Side Switch for an LED:
This is the most common application. The microcontroller GPIO pin (e.g., outputting 3.3V or 5V) is connected to the Gate through a current-limiting resistor (typically 100Ω). The load (an LED in series with a current-limiting resistor) is connected between the positive supply (Vdd) and the Drain pin. The Source pin is connected to ground. When the microcontroller output is HIGH, the MOSFET turns on, completing the circuit and illuminating the LED. This circuit effectively isolates the sensitive microcontroller from the higher voltage/current load.
2. Driving a Relay Coil:
Relay coils are inductive loads that require more current than a microcontroller can provide. The BSS123NH6327 acts as a perfect interface. The coil is placed between the power supply and the Drain pin. A flyback diode (or freewheeling diode) is critical in this circuit and must be placed in reverse bias across the relay coil to suppress the voltage spike generated when the inductive load is switched off, protecting the MOSFET from damage.
3. PWM Motor Speed Control:
For small DC motors, the BSS123NH6327 can be used in conjunction with a microcontroller's Pulse Width Modulation (PWM) output. The fast switching capability of the MOSFET allows it to efficiently turn on and off at high frequencies, varying the average power delivered to the motor and thus controlling its speed. A diode is also used here to protect against back EMF from the motor's inductance.
ICGOOODFIND: The Infineon BSS123NH6327 stands out as an exceptionally efficient and reliable logic-level switch. Its robust performance, defined by a low gate threshold voltage and compact SMD footprint, makes it an ideal choice for designers seeking to interface digital control units with various real-world loads. Its versatility in applications ranging from simple LED drivers to inductive load controllers underscores its fundamental role as a building block in electronic design.
Keywords: Logic Level MOSFET, Low-Side Switch, SOT-23, Fast Switching, Enhancement Mode.
