onsemi MMBTA64

Overview

MMBTA64 from ON Semiconductor is a PNP Darlington transistor in SOT-23 package, designed for high-current-gain switching and amplification up to 800 mA collector current, with V_CEO = −30 V, h_FE ≥ 10,000 at I_C = −10 mA, and V_CE(sat) = −1.5 V at I_C = −100 mA / I_B = −0.1 mA. It serves in low-frequency power control circuits such as relay drivers and lamp dimmers.

For engineers reviewing the MMBTA64 datasheet, pinout, applications, or equivalent options, key selection criteria include guaranteed high h_FE at medium currents, low saturation voltage under Darlington configuration, thermal performance in SOT-23, and compatibility with legacy Fairchild-designated PCB footprints.

Technical Context

The MMBTA64 implements a monolithic PNP Darlington pair with integrated base-emitter resistor network absent-requiring external base drive control. Its architecture delivers high DC current gain (h_FE ≥ 20,000 max at I_C = −100 mA) while maintaining V_CE(sat) ≤ −1.5 V under specified test conditions.

It operates across −55°C to +150°C junction temperature range, with R_θJA = 357°C/W on FR-4 PCB, and is rated for continuous collector current of −1.2 A and total power dissipation of 350 mW at 25°C ambient-derating linearly by 2.8 mW/°C above that point.

Key Specifications

Pinout & Package

SOT-23 surface-mount plastic package (3-lead, JEDEC MO-178AA), marked "2V", with lead frame plating per J-STD-020 moisture sensitivity level 1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with PN2907A and ZTX951, the MMBTA64 uniquely balances SOT-23 form factor, guaranteed h_FE ≥ 10,000 at −100 mA, −30 V rating, and −1.2 A current capability-making it optimal for compact, high-gain, medium-voltage switching where thermal management is constrained.

Availability

MMBTA64 is available at Aetrix Electronics and suitable for relay driver circuits, lamp dimming controls, motor start assist circuits, and industrial sensor interface outputs requiring stable component supply and long-term manufacturability.

Supply support for MMBTA64 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 is a global semiconductor manufacturer specializing in energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, medical, and consumer markets.

The MMBTA64 belongs to ON Semiconductor's legacy discrete bipolar transistor portfolio, originally developed by Fairchild Semiconductor to serve high-reliability, high-gain switching applications in industrial control and appliance power stages.

FAQ

What is the maximum continuous collector current rating for the MMBTA64?

The MMBTA64 is rated for a maximum continuous collector current (I_C) of −1.2 A at T_A = 25°C, with linear derating of 2.8 mW/°C above that ambient temperature. This rating assumes proper PCB copper area for thermal conduction and accounts for the device's 350 mW total power dissipation limit. Actual usable current depends on layout, airflow, and ambient conditions-designers should verify junction temperature remains below 150°C in final application.

Does the MMBTA64 have an integrated base resistor?

No, the MMBTA64 does not include an integrated base resistor. It is a bare PNP Darlington transistor requiring external base current limiting-typically via a series resistor between the driving source and the base pin. This design allows flexible biasing for both switching and linear operation, unlike digital transistors (e.g., MMBT2222A with built-in resistors). The absence of internal resistors also preserves full control over h_FE utilization and switching speed.

What is the typical V_BE(on) of the MMBTA64 at I_C = −100 mA?

The MMBTA64 exhibits a typical base-emitter on voltage (V_BE(on)) of −2.0 V at I_C = −100 mA and V_CE = −5.0 V, per its official datasheet. This reflects the stacked V_BE drop of two PNP junctions in Darlington configuration. Designers must ensure driver circuits can supply sufficient negative base current to overcome this threshold-e.g., −0.1 mA base current yields −100 mA collector current with h_FE ≈ 1000.

Can the MMBTA64 replace the MPSA64 in existing designs?

The MMBTA64 is not a direct pin-compatible replacement for the MPSA64 due to differing packages: MPSA64 uses TO-92 while MMBTA64 uses SOT-23. Electrical characteristics are closely matched (same V_CEO, h_FE, and V_CE(sat) specs), but PCB layout revision is required to accommodate the surface-mount footprint. For new designs prioritizing miniaturization and automated assembly, MMBTA64 is preferred; for through-hole legacy repairs, MPSA64 remains appropriate.

Is the MMBTA64 suitable for linear amplification applications?

Yes, the MMBTA64 supports linear-mode operation with verified h_FE stability and predictable V_CE(sat) and V_BE(on) behavior across temperature. Its f_T of 125 MHz and low noise profile make it viable for audio preamplifier stages and sensor signal conditioning-provided biasing avoids saturation and power dissipation stays within 350 mW limits. Thermal design remains critical, especially at high quiescent currents.