onsemi MMBTA55

Overview

MMBTA55 from Fairchild Semiconductor is a PNP bipolar junction transistor designed for general-purpose amplifier and switching applications up to 300 mA collector current, featuring -60 V V_CEO, 100 minimum h_FE at -10 mA, and 50 MHz f_T, commonly used in low-power signal amplification stages of consumer audio and power management circuits.

For engineers reviewing the MMBTA55 datasheet, pinout, applications, or equivalent options, key selection considerations include its SOT-23 package compatibility, PNP polarity, -60 V breakdown rating, thermal derating (2.8 mW/°C), and verified operation across -55°C to +150°C junction temperature range.

Technical Context

The MMBTA55 operates as a silicon PNP BJT with fixed emitter-base and collector-base junction structures optimized for linear amplification and saturated switching. Its DC current gain (h_FE) is specified at two operating points: ≥100 at -10 mA and ≥100 at -100 mA, indicating stable gain over a 10× collector current range.

It exhibits a -0.25 V V_CE(sat) at -100 mA/-10 mA drive and -1.2 V V_BE(on) under same conditions, confirming low-saturation performance suitable for discrete gain blocks and level-shifting circuits where base drive efficiency matters.

Key Specifications

Pinout & Package

SOT-23 (TO-236AB) 3-lead surface-mount package with gull-wing leads; standardized footprint per JEDEC MO-178, land pattern recommended per MA03D drawing.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP general-purpose amplifier applications.

Compared with MMBTA55, MMBTA56 serves complementary NPN roles in dual-rail circuits, while BC807-40 offers higher gain at reduced voltage rating-making MMBTA55 optimal for cost-sensitive, medium-gain, -60 V tolerant PNP applications where thermal margin and polarity specificity matter.

Availability

MMBTA55 is available at Aetrix Electronics and suitable for audio pre-amplifier stages, discrete level shifters, and low-power switch drivers requiring stable component supply and long-term industrial availability.

Supply support for MMBTA55 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

Fairchild Semiconductor was a U.S.-based semiconductor manufacturer specializing in power management, analog, and discrete components before its acquisition by ON Semiconductor in 2016.

The MMBTA55 belongs to Fairchild's legacy general-purpose BJT product line, engineered for cost-effective, reliable amplification and switching in consumer, industrial, and computing applications.

FAQ

What is the maximum collector-emitter voltage rating for the MMBTA55?

The MMBTA55 has a guaranteed V_CEO rating of -60 V at T_A = 25°C, meaning it can safely withstand up to 60 volts of reverse bias between collector and emitter with base open. This rating is based on a maximum junction temperature of 150°C and applies to continuous DC operation; pulsed conditions require consultation with Fairchild's application engineering team. The MMBTA55 must not be operated beyond this limit to avoid permanent damage.

Is the MMBTA55 suitable for switching applications?

Yes, the MMBTA55 is suitable for low-to-medium speed switching applications, evidenced by its -0.25 V V_CE(sat) at -100 mA/-10 mA drive and 50 MHz f_T. It supports clean turn-on/turn-off in discrete load control circuits such as LED drivers or relay interfaces. However, it is not optimized for high-frequency PWM or RF switching; for those uses, dedicated MOSFETs or faster BJTs should be considered. The MMBTA55 remains a robust choice for <100 kHz switching with moderate current demands.

What package type does the MMBTA55 use?

The MMBTA55 uses the SOT-23 (TO-236AB) 3-lead surface-mount package, marked "2H" on the top surface. Its mechanical dimensions conform to JEDEC MO-178 standards, with a 2.40 mm × 1.30 mm body and 0.95 mm lead pitch. The package supports automated pick-and-place assembly and reflow soldering per IPC-J-STD-020. Thermal resistance is specified at 357 °C/W junction-to-ambient on a standard FR-4 PCB, making thermal pad design critical for sustained >200 mA operation.

How does the MMBTA55 compare to the MMBTA42?

The MMBTA42 is an NPN counterpart to the PNP MMBTA55, sharing identical SOT-23 packaging, absolute maximum ratings (-60 V V_CEO, 500 mA I_C), and thermal characteristics. Both exhibit h_FE ≥100 at -10 mA (MMBTA55) or +10 mA (MMBTA42). Their complementary polarity makes them ideal for matched pair designs like differential amplifiers or push-pull output stages. The MMBTA55 and MMBTA42 are often used together in the same schematic, enabling symmetrical biasing and signal handling.

What is the DC current gain (h_FE) specification for the MMBTA55?

The MMBTA55 guarantees h_FE ≥100 at both -10 mA and -100 mA collector current, with V_CE = -1.0 V and T_A = 25°C. This flat gain curve across a decade of current supports consistent amplification in varying load conditions without requiring gain-stabilizing emitter resistors in many cases. The MMBTA55's h_FE is measured under standardized pulse test conditions (≤300 μs pulse width, ≤2% duty cycle) to minimize self-heating effects during characterization.