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BSS138 N-Channel Logic Level MOSFET

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The BSS138 is an SMD Package Logic Level N-Channel MOSFET with low on-state resistance (3.5Ω) and low input capacitance (40 pF). Adding to this the Mosfet can also switching at high speed of 20ns. Due to the low threshold voltage and high switching speed this Mosfet is commonly used in level shifter circuits.


Pin Configuration

Pin Number

Pin Name




Current flows out through Source



Controls the biasing of the MOSFET



Current flows in through Drain



  • Logic Level N-Channel MOSFET with low on-state resistance
  • Continuous Drain Current (ID) is 200mA
  • Drain Source Voltage (VDS) is 50V
  • On-state Resistance is 3.5Ω
  • Minimum Gate threshold voltage (VGS-th) is 0.5V
  • Maximum Gate threshold voltage (VGS-th) is 1.5V
  • Turn ON and Turn off time is 20ns each
  • Available in SOT23 SMD package

Note: The complete technical information can be found at the BSS138 datasheet given at the end of this page.


Alternative for BSS138 MOSFET

NTR4003, 2N7002, FDC666, FDC558, BS170, 2N7000


BSS138 Equivalent P-Channel MOSFET

BSS84, FDN358P


Other N-Channel MOSFETs

BS170N, IRF3205, 2N7000, IRF1010E, IRF540N


BSS138 MOSFET Overview

The BSS138 is a compact Logic Level N-Channel Mosfet. The mosfet has very low threshold voltage of 0.5V and hence can be used with any low voltage application circuits and for level shifting applications. Adding to this the Mosfet also has low on-state resistance and low input capacitance which makes it efficient in switching circuits. Because of the compact nature of the mosfet it is widely used in portable applications like Cellular phones and other power management circuits.

The BSS138 is slightly expensive for its specification, so if you are looking for a cheap alternative do check 2N7002. However you have to compensate slightly with the on-state resistance and threshold voltage of the Mosfet. This mosfet comes in a SMD package hence can be used for compact applications. One considerable disadvantage of the mosfet is its low drain current; it can provide a continuous current of 200mA and peaks currents upto 1A at maximum threshold voltage. Anything more than that will damage the mosfet.


BSS138 Applications

  • Low current and Low Voltage switching applications
  • Logic Level Shifters
  • DC-DC converts
  • eMobility applications
  • Application where low on-state resistance is required.
  • Power management applications



The Mosfet is available in SOT23 and TO-92 package, the dimensions of the SOT23 package is shown below. Refer the BSS138 datasheet below for other dimensions.

BSS138 Dimensions

Component Datasheet