onsemi MPSA28G

Overview

MPSA28G from onsemi is an NPN silicon Darlington transistor in TO-92 package, rated for 80 V_CE, 500 mA continuous collector current, and 625 mW power dissipation at 25°C ambient. It delivers high DC current gain (h_FE ≥ 10,000 at I_C = 10 mA), low V_CE(sat) (≤ 0.7 V at I_C/I_B = 10 mA/0.01 mA), and operates across −55°C to +150°C junction temperature - used in low-speed switching and signal amplification circuits requiring high input impedance and current gain.

For engineers reviewing the MPSA28G datasheet, pinout, applications, or equivalent options, key selection criteria include its Darlington configuration, TO-92 leaded package, 80 V breakdown rating, 10,000 minimum h_FE, and Pb-free compliance - critical for industrial control interfaces, relay drivers, and analog sensor front-ends where base drive efficiency and thermal margin matter.

Technical Context

The MPSA28G integrates two cascaded NPN transistors in a monolithic Darlington pair, delivering ultra-high current gain while maintaining single-package simplicity. Its structure enables microampere-level base drive to switch 500 mA loads, with V_BE(on) up to 2.0 V and V_CE(sat) ≤ 1.2 V under full-rated current.

Designed for linear and switching operation in ambient temperatures up to +25°C (derated above), it features R_JA = 200°C/W and R_JC = 83.3°C/W thermal resistance. The device supports safe operating area (SOA) up to 100 mA at 50 V in active region and withstands transient conditions per pulse test specifications (300 µs, 2% duty cycle).

Key Specifications

Pinout & Package

Package: TO-92 (Case 29-11), through-hole, Pb-free, 3-pin plastic package with Emitter/Base/Collector pinout (pin 1 = Emitter, pin 2 = Base, pin 3 = Collector).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar Darlington transistor applications.

Compared with MPSA28G, MPSA29G offers higher voltage tolerance without trade-offs in gain or thermal performance, while ULN2003A provides integration benefits at the cost of discrete flexibility and voltage headroom - making MPSA28G optimal for cost-sensitive, single-load, 80 V-class switching where layout simplicity matters.

Availability

MPSA28G is available at Aetrix Electronics and suitable for relay drivers, LED regulators, linear amplifiers, and power supply enable switches requiring stable component supply, long-term manufacturability, and RoHS-compliant through-hole assembly.

Supply support for MPSA28G 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier focused on energy-efficient technologies for automotive, industrial, cloud, and IoT applications.

The MPSA28G belongs to onsemi's general-purpose bipolar transistor product line, designed specifically for cost-effective, high-gain switching and amplification in industrial controls, instrumentation, and legacy-compatible systems.

FAQ

What is the maximum collector-emitter voltage rating for MPSA28G?

The MPSA28G has a guaranteed minimum collector-emitter breakdown voltage (V_(BR)CES) of 80 Vdc at I_C = 100 µAdc and V_BE = 0. This rating defines the absolute maximum DC voltage that can be applied between collector and emitter while keeping the device in cutoff. Exceeding this value risks irreversible avalanche failure. Designers should maintain at least 20% derating margin - i.e., limit steady-state V_CE to ≤64 V - especially in inductive load switching applications where voltage spikes occur.

Does MPSA28G require a base resistor when driven by a microcontroller GPIO?

Yes, MPSA28G requires an external base resistor to limit base current and ensure proper saturation. With typical V_BE(on) ≈ 1.4–2.0 V and target I_B = 0.01 mA for 10 mA I_C, a 330 Ω resistor is appropriate for a 3.3 V GPIO, and 470 Ω for 5 V. Omitting the resistor risks excessive base current, thermal runaway, and premature device failure. The MPSA28G's Darlington structure does not eliminate the need for current limiting - it only increases current gain.

Is MPSA28G pin-compatible with MPSA29G?

Yes, MPSA28G and MPSA29G share identical TO-92 package dimensions, pinout (Emitter/Base/Collector on pins 1/2/3), and mechanical mounting. Both comply with Case 29-11 and have the same lead spacing and orientation. This allows direct substitution in existing layouts without PCB modification - though designers must verify that the higher 100 V rating of MPSA29G does not introduce unintended interaction with surrounding circuitry, such as reduced base drive margin due to higher V_BE variation.

What is the thermal resistance junction-to-ambient (R_JA) for MPSA28G in free-air conditions?

The MPSA28G has a specified R_JA of 200°C/W under standard JEDEC test conditions (single device on FR-4 board, 1-inch² copper pad, no airflow). This means each watt of power dissipated raises the junction temperature by 200°C above ambient. At its rated 625 mW maximum dissipation, junction temperature rises ~125°C above ambient - so operation above 25°C ambient requires careful thermal design. For sustained 500 mW loads, ambient must stay below 25°C or supplemental cooling must be added to avoid exceeding the +150°C T_J limit.

Can MPSA28G be used in linear amplifier configurations?

Yes, MPSA28G is qualified for linear operation with verified small-signal parameters including f_T = 125 MHz and C_obo = 5.0–8.0 pF. Its high h_FE and low noise characteristics support Class-A preamplifier use in audio and sensor signal chains. However, designers must ensure DC bias stability via emitter degeneration, limit power dissipation to stay within SOA boundaries (see Figure 5), and avoid operation near second breakdown limits - particularly at high V_CE and moderate I_C. The MPSA28G datasheet confirms active-region performance down to 1 mA I_C.