Diodes Incorporated BSS138-7

Overview

BSS138-7 from Diodes Incorporated is an N-channel enhancement-mode vertical DMOS FET in SOT23 package, rated for 50 V V_DS, 200 mA continuous drain current, and 3.5 Ω R_DS(on) at V_GS = 5 V; used as a low-side load switch in portable logic-level interface circuits.

For engineers reviewing the BSS138-7 datasheet, BSS138-7 pinout, BSS138-7 application, or BSS138-7 equivalent, key selection criteria include gate threshold voltage (0.5–1.5 V), low input capacitance (C_iss = 50 pF), fast switching (t_r/t_f ≤ 10/25 ns), and SOT23 thermal performance under pulsed 200 mA loads.

Technical Context

This discrete MOSFET operates in enhancement mode with a vertically structured DMOS cell, enabling low on-resistance and fast turn-on/off transitions under logic-level gate drive (≥2.5 V). Its gate threshold voltage range (0.5–1.5 V) ensures reliable turn-on with 3.3 V and 5 V microcontroller I/O.

Designed for low-power switching, it features low gate charge (Q_g ≈ 1.5 nC at V_GS = 5 V, inferred from typical gate charge curve), minimal output capacitance (C_oss = 25 pF), and specified operation up to +150 °C junction temperature.

Key Specifications

Pinout & Package

SOT23-3 surface-mount package with gull-wing leads; compact footprint (2.9 × 1.3 × 1.0 mm), JEDEC TO-236AB compliant, rated for 360 mW power dissipation at 25 °C ambient.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar N-channel logic-level switching applications.

Compared with 2N7002-7 and DMN2004K-7, BSS138-7 offers the best balance of low-threshold certainty, moderate R_DS(on), and minimal C_iss-ideal for high-speed, low-voltage, low-power digital switching where timing predictability and gate drive simplicity are critical.

Availability

BSS138-7 is available at Aetrix Electronics and suitable for LED indicator control, microcontroller I/O expansion, and portable sensor load switching requiring stable component supply across industrial and consumer production cycles.

Supply support for BSS138-7 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, headquartered in Plano, Texas, with design and manufacturing operations across Asia and the Americas.

The BSS138-7 belongs to Diodes' general-purpose small-signal MOSFET product line, engineered for logic-level switching in space-constrained, low-power digital and mixed-signal systems.

FAQ

Is BSS138-7 suitable for 1.8 V GPIO drive?

Yes. With a guaranteed V_GS(th) as low as 0.5 V and typical R_DS(on) ≤ 5.5 Ω at V_GS = 1.8 V (per normalized curves), BSS138-7 achieves usable conduction at 1.8 V logic levels-confirmed by transfer characteristic plots showing >10 mA I_D at V_GS = 1.8 V and V_DS = 2 V.

What is the maximum safe pulsed drain current?

The absolute maximum pulsed drain current is 800 mA, specified under pulse conditions (width = 300 µs, duty cycle ≤ 2%). This rating assumes proper PCB copper area for thermal dissipation and applies only when junction temperature remains within –55 °C to +150 °C limits per pulse.

Does BSS138-7 have avalanche rating?

No. The datasheet does not specify avalanche energy (E_AS) or repetitive avalanche ratings. It is not designed for unclamped inductive switching; external flyback protection (e.g., Schottky clamp) is required when driving relays or solenoids.

Can BSS138-7 replace BS170 in existing designs?

Not directly. BS170 has higher V_DS (60 V), higher I_D (500 mA), and TO-92 packaging. BSS138-7 offers lower R_DS(on) and SOT23 footprint but reduced voltage/current headroom; redesign verification is required for voltage margin, thermal layout, and gate drive compatibility.