Diodes Incorporated MMBTA42-7

Overview

MMBTA42-7 from Diodes Incorporated is an NPN small-signal surface-mount transistor with 300 V VCBO, 300 V VCEO, and 500 mA IC rating, built using epitaxial planar die construction for medium-power amplification and switching in high-voltage interface stages of industrial power supplies and relay drivers.

For engineers reviewing the MMBTA42-7 datasheet, MMBTA42-7 pinout, MMBTA42-7 application, or MMBTA42-7 equivalent, key selection criteria include its 300 V breakdown voltage capability, 50 MHz fT bandwidth, SOT-23 package thermal resistance (417 K/W), and verified hFE range of 25–40 at 1–30 mA collector current.

Technical Context

The MMBTA42-7 operates as a general-purpose NPN bipolar junction transistor optimized for linear amplification and saturated switching in high-voltage, low-to-medium current circuits. Its 300 V collector-base and collector-emitter breakdown ratings enable use in flyback snubbers and HV bias rails where standard 60–80 V transistors fail.

It delivers 50 MHz current gain–bandwidth product at 10 mA/20 V bias and maintains usable hFE down to –50°C and up to +150°C, supporting operation across extended industrial temperature ranges without gain collapse or secondary breakdown.

Key Specifications

Pinout & Package

Package: SOT-23 - ultra-compact surface-mount plastic case (UL 94V-0 rated), 3-pin configuration with gull-wing leads, footprint compatible with JEDEC TO-236AB standard.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN high-voltage switching applications.

Compared with MMBTA42-7, MMBTA44-7 offers greater voltage headroom but reduced hFE consistency at low currents, while BC846B-7 sacrifices all high-voltage capability for precision gain-making MMBTA42-7 the optimal balance for 200–300 V industrial interface designs.

Availability

MMBTA42-7 is available at Aetrix Electronics and suitable for industrial relay drivers, high-voltage bias supplies, and programmable logic interfaces requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for MMBTA42-7 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 centers across Asia and manufacturing in China, Taiwan, and the US.

The MMBTA42-7 belongs to Diodes' small-signal transistor portfolio designed specifically for high-reliability industrial and automotive interface applications demanding extended voltage and temperature performance.

FAQ

What is the maximum continuous collector current for MMBTA42-7 at 70°C ambient?

At TA = 70°C, the MMBTA42-7's maximum continuous collector current is 375 mA. This is derived from its 300 mW power dissipation limit and 417 K/W thermal resistance: Pd = (Tj_max − TA)/RJA = (150 − 70)/417 ≈ 0.192 W, and IC_max = √(Pd × RCE(SAT)⁻¹) ≈ 375 mA assuming typical VCE(SAT) of 0.5 V. Derating follows the curve in Figure 1 of DS30062 Rev. 6.

Can MMBTA42-7 be used in linear amplifier configurations?

Yes - the MMBTA42-7 supports Class-A and Class-AB linear amplification with verified hFE stability from 1 mA to 30 mA and fT = 50 MHz at 10 mA. Its low noise figure (<10 dB at 1 kHz) and consistent gain across –55°C to +150°C make it suitable for preamplifier stages in industrial sensor signal chains where high-voltage common-mode rejection is needed.

Is the SOT-23 package of MMBTA42-7 compatible with automated pick-and-place equipment?

Yes - the MMBTA42-7 uses standard JEDEC TO-236AB-compliant SOT-23 packaging with gull-wing leads, 0.95 mm pitch, and defined land pattern per Diodes' AP02001. It is qualified for high-speed placement at ≥25,000 UPH and withstands reflow per J-STD-020A Level 1 (peak 260°C), including lead-free profiles.

Does MMBTA42-7 have a complementary PNP counterpart?

Yes - the MMBTA92 is the designated complementary PNP device, sharing identical SOT-23 package, 300 V breakdown ratings (VCBO/VCEO), and matching thermal characteristics. Both are specified for use in push-pull amplifier outputs and dual-rail switching circuits where matched gain and voltage capability are critical.