onsemi MMBTA56

Overview

MMBTA56 from ON Semiconductor is a PNP bipolar junction transistor (BJT) designed for general-purpose amplification and switching at collector currents up to 500 mA. It features -80 V V_CEO, -80 V V_CBO, -4.0 V V_EBO, DC current gain (h_FE) ≥100 at -10 mA, and operates across -55°C to +150°C. It is commonly used in low-power audio preamplifiers, level-shifting circuits, and discrete logic interface stages.

For engineers reviewing the MMBTA56 datasheet, pinout, applications, or equivalent options, key selection criteria include its SOT-23 package footprint, PNP polarity, thermal resistance of 357°C/W, saturation voltage of -0.25 V at -100 mA/-10 mA, and suitability for space-constrained consumer and industrial control boards requiring discrete gain or switching.

Technical Context

The MMBTA56 is a silicon planar epitaxial PNP transistor fabricated using Fairchild's Process 73, optimized for stable DC current gain and low saturation voltage in general-purpose linear and switching roles. Its structure supports operation with base-emitter forward bias and collector-emitter reverse bias configurations typical in active-load amplifiers and high-side switch drivers.

It functions as a single-ended, medium-speed amplifier with f_T = 50 MHz at -100 mA and V_CE = -1.0 V, enabling use in sub-10 MHz signal conditioning and pulse amplification. Thermal performance is defined for FR-4 PCB mounting with 6 cm² collector pad area, limiting continuous power dissipation to 350 mW at 25°C ambient.

Key Specifications

Pinout & Package

MMBTA56 is housed in a JEDEC-standard SOT-23 (TO-236AB) 3-lead surface-mount plastic package with marking "2G". The package measures 2.92 mm × 1.30 mm × 1.00 mm and is optimized for automated placement and reflow soldering on compact PCBs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MMBT3906 and BC807-40, the MMBTA56 uniquely balances −80 V breakdown, guaranteed h_FE ≥100 at −10 mA, and SOT-23 compatibility-making it optimal for industrial-level shifting and 24 V+ analog front-ends where both voltage headroom and gain consistency matter.

Availability

MMBTA56 is available at Aetrix Electronics and suitable for industrial sensor interfaces, microcontroller logic translation, and low-power audio preamplification requiring stable component supply and long-term manufacturability.

Supply support for MMBTA56 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

ON Semiconductor (formerly Fairchild Semiconductor) is a global supplier of energy-efficient semiconductor solutions for automotive, industrial, cloud computing, and IoT applications.

The MMBTA56 belongs to ON Semiconductor's general-purpose bipolar transistor product line, engineered for cost-sensitive, high-volume applications demanding proven reliability, wide temperature operation, and standardized SMT packaging.

FAQ

What is the maximum collector-emitter voltage rating for MMBTA56?

The MMBTA56 has a V_CEO rating of −80 V, meaning it can safely block up to 80 V in reverse bias between collector and emitter with base open. This rating is confirmed in the Absolute Maximum Ratings table and applies at T_A = 25°C. Exceeding this voltage risks avalanche breakdown and permanent device failure. Always derate for temperature and transient conditions per the datasheet guidelines.

Is MMBTA56 pin-compatible with MMBT3906?

Yes, the MMBTA56 is pin-compatible with the MMBT3906 in the SOT-23 package: Emitter (Pin 1), Base (Pin 2), Collector (Pin 3). However, MMBTA56 offers higher voltage ratings (−80 V vs. −40 V) and guaranteed h_FE ≥100 at −10 mA, whereas MMBT3906 specifies h_FE ≥100 only at −1 mA. Substitution requires verifying voltage margin in the target circuit.

What is the thermal resistance (R_θJA) of MMBTA56 and how does it affect layout?

The MMBTA56 has an R_θJA of 357°C/W when mounted on a standard FR-4 PCB with a 6 cm² copper pad under the collector lead. This high value means even modest power dissipation (e.g., 100 mW) raises junction temperature by ~36°C above ambient. To maintain reliability, PCB layout must maximize copper area connected to Pin 3 (collector) and avoid thermal isolation.

Does MMBTA56 support operation at elevated temperatures like +125°C?

Yes, the MMBTA56 is rated for operation from −55°C to +150°C junction temperature. At +125°C ambient, its usable power dissipation drops significantly due to thermal derating (2.8 mW/°C above 25°C), limiting continuous I_C to ~60 mA with standard layout. For such environments, verify actual T_J using measured board temperature and R_θJA.

What is the typical current gain-bandwidth product (f_T) of MMBTA56 and under what conditions is it measured?

The MMBTA56 has a typical f_T of 50 MHz, measured at I_C = −100 mA, V_CE = −1.0 V, and f = 100 MHz. This indicates usable small-signal amplification bandwidth up to ~5–10 MHz in practical common-emitter configurations. Gain rolls off at 20 dB/decade beyond f_T, so high-frequency stability requires careful compensation in feedback designs.