Part Number: BSS138PW

Manufacturer: Nexperia

Description: MOSFET BSS138PW/SOT323/SC-70

Shipped from: Shenzhen/HK Warehouse

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We have been familiar with several 3.3V devices, including the ESP32, ESP8266, HC-05 Bluetooth module, BMP180 barometric pressure sensor,  Nokia 5110 LCD, etc., for a long time. Use a logic level shifter or an external level shifter to link a 3.3V SPI or I2C device to a 5 Volt Arduino or other devices that support bi-directional communication. To provide bidirectional level shifting and shield the low voltage side from the high voltage side, the logic level shifter requires one BSS138 MOSFET per bus. This article gives a quick overview of the BSS138 N-channel logic level MOSFET.

BSS138PW MOSFET Overview

The Logic Level N-Channel Mosfet BSS138PW is a small device. Because of its extremely low 0.5V threshold voltage, the MOSFET can be employed in level-shifting applications and with any low-voltage application circuit. The Mosfet is effective in switching circuits due to its low input capacitance and low on-state resistance, which are additional features. The MOSFET is frequently utilized in portable applications like cellular phones and other power management circuits because of its slim design.

The BSS138 is somewhat pricey, given its specifications, so if you’re searching for a less-priced option, consider the 2N7002. You must make a small adjustment with the Mosfet’s threshold voltage and on-state resistance. Because it is in an SMD package, this MOSFET can be employed in small applications. The MOSFET has a significant drawback: it has a low drain current, with continuous currents of 200mA and peak currents of 1A at the maximum threshold voltage. The MOSFET will be harmed by anything more.

BSS138PW Features and Benefits

  • High-speed switching
  • Logic-level compatible
  • ESD protection up to 1.5 kV
  • Trench MOSFET technology
  • AEC-Q101 qualified

BSS138PW Applications

  • Relay driver
  • High-speed line driver
  • Low-side load switch
  • Switching circuits

Circuit Diagram?

By examining the circuit diagram, see how to implement a bidirectional level shifter using an N-channel BSS138PW logic level MOSFET. Look at the circuit below, which includes a BSS138 N-channel MOSFET and an internal drain-substrate diode (one must be present). The left or low voltage and the right, or high voltage, halves of the circuit should be separated.

Different logic levels and supply voltages are present on each side. The device power supply is 3.3 Volts when the bus on the low voltage side is pulled to HIGH. The device power and the bus on the right side are HIGH at 5 volts. A low voltage supply of 3.3 V needs to be connected to the MOSFET’s gate terminal. The low- and high-voltage buses are connected to the MOSFET’s source and drain terminals. A bidirectional logic level shifter is what this straightforward circuit does.

Let’s now examine how the circuit described above functions as a bi-directional logic level converter. Let’s break the task’s functioning into 3 states to get a clearer idea.

Standby State

First, when there is no signal from either side, it will produce a strong output signal or accept it as an input. This means that nothing exists to lower the signal level; thus, we must pull the output to a high logic at both ends (for instance, 3.3V for Raspberry Pi and 5V for Arduino).

The MOSFET is OFF because the gate-to-source junction voltage, measured at pins 1 and 2, is 0V (3.3V on both). As a result, the output at the LV1 site is based on resistor R1, which has a 3.3V pull-up capability, while the production is based on R2, which has a 5V pull-up capability. Therefore, both endpoints are more logically sound.

3.3Volts Side is Pulled Low

The low voltage output can be obtained by connecting the output to 0V through an open drain. This causes the gate terminal of the Q1 source to be pulled up to 0V and 3.3V, turning on the MOSFET. When this happens, Q1’s high output (at the gate terminal) turns low. So this leads to a low-level logic output on the high-voltage side.

5 Volts side is Pulled Low

Now let’s know how to pull the bus low to handle the transition from a high level on both sides to the 5V side. The low voltage output can be obtained by connecting the output to 0V through an open drain. For current to move from the source to the drain, the MOSFET’s drain-substrate diode substrate is pulled down (opposite to the conducting current when it works as a switch).

The MOSFET turns ON when the voltage between the source and the gate dips below that threshold. LV and HV sides are both at 0V while the MOSFET is in the ON state, delivering a logic low level on either side.

It functions as a bidirectional logic level shifter when all three states are coupled since the logic levels can be altered in both directions.

Applications of BSS138PW

The following are the applications of BSS138PW.

  • They are used in applications with low voltage and low current.
  • They are utilized in circuits for bidirectional logic level shifters.
  • A component of DC-DC converters.
  • They are utilized in applications that call for minimal on-state resistance.
  • Used in applications for e-mobility
  • Used in applications for power management.

Frequently Asked Questions (FAQ)

What are the benefits of using 200-300 V BSS138W?

The most recent Infineon 200-300 V BSS138W is tailored for high current and low RDS(on), making it ideal for industrial applications. The flagship IRF200P222 has a 40% higher current carrying capacity and a 32% lower RDS(on) compared to previous generation devices, leading to a higher power density and fewer I2R losses.

175°C package of OptiMOS™ 5 Power MOSFETs in BSS138W: Advantages?

The 175°C TJ MAX provides greater power at a higher operating junction temperature and has a longer lifespan at the same operating junction temperature. It also has the highest system reliability. Thermostability Highest efficiency and power density

How does BSS138W operating temperature range?

BSS138W can operate in temperatures between -55°C and 150°C TJ.


Thus, this is all about an overview of BSS138PW N-channel logic-level MOSFET. These are designed to minimize the on-state resistance and provide fast switching performance. These are more reliable and rugged types used in low current and low voltage applications such as servo motor control, power drive circuit, and other switching applications.

If you need information or want to order BSS138PW, contact us here at ICRFQ, your leading electronic components in china, and we will ensure you get the best product at the best price.

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