onsemi MMBTA55LT3

Overview

MMBTA55LT3 from onsemi is a PNP silicon small-signal transistor in SOT-23 package, rated for −60 V V_CEO, −500 mA I_C, and 225 mW power dissipation on FR-5 board. It delivers h_FE ≥ 100 at −10 mA I_C, V_CE(sat) ≤ −0.25 V at −100 mA/−10 mA drive, and f_T = 50 MHz - used in low-power switching and linear amplification stages of portable power management and signal conditioning circuits.

For engineers reviewing the MMBTA55LT3 datasheet, pinout, applications, or equivalent options, key selection criteria include verified PNP polarity, SOT-23 terminal mapping (Pin 1 = Base, Pin 2 = Emitter, Pin 3 = Collector), −60 V breakdown rating, DC gain stability across −55°C to +150°C, and Pb-free compliance per J-STD-609.

Technical Context

This discrete PNP transistor operates in active, saturation, and cutoff regions with defined V_BE(on) ≤ −1.2 V and V_CE(sat) ≤ −0.25 V under −100 mA/−10 mA bias. Its f_T = 50 MHz supports RF-coupled preamp and high-speed switching up to ~10 MHz with controlled rise/fall times (t_r = 3.0 ns).

Thermal design relies on R_JA = 556°C/W (FR-5) or 417°C/W (alumina), with derating of 1.8 mW/°C above 25°C. Junction temperature range (−55°C to +150°C) and guaranteed V_(BR)CEO = −60 V ensure reliability in automotive body electronics and industrial sensor interfaces.

Key Specifications

Pinout & Package

SOT-23 (Case 318, Style 6) surface-mount plastic package with gull-wing leads; dimensions per ON Semiconductor CASE 318-08 (0.95 mm max height, 2.90 mm length, 1.30 mm width).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP small-signal transistor applications.

Compared with MMBTA55LT3, MMBTA55LT1G offers identical performance in a smaller reel format, while PN2907A trades SMT scalability and fine-grain gain control for through-hole serviceability - making MMBTA55LT3 optimal for high-density, high-volume automated assembly with precise low-current gain requirements.

Availability

MMBTA55LT3 is available at Aetrix Electronics and suitable for LED driver circuits, level-shifting interfaces, power supply enable switches, and industrial sensor signal conditioning requiring stable component supply and full traceability.

Supply support for MMBTA55LT3 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 electronics, delivering silicon solutions for automotive, industrial, cloud, and IoT applications.

The MMBTA55LT3 belongs to onsemi's broad portfolio of general-purpose bipolar transistors designed for cost-sensitive, high-reliability discrete signal switching and amplification in consumer, industrial, and automotive systems.

FAQ

What is the maximum continuous collector current rating for MMBTA55LT3?

The MMBTA55LT3 has a maximum continuous collector current (I_C) rating of −500 mA at T_A = 25°C. This value assumes adequate PCB copper area for heat dissipation; derating applies above 25°C at 1.8 mW/°C on FR-5 board. Actual usable current depends on V_CE, duty cycle, and thermal environment - for example, sustained −300 mA operation requires ≤ 65°C ambient with 1-in² 2-oz copper pour.

Is MMBTA55LT3 pin-compatible with MMBTA56LT3?

No, MMBTA55LT3 and MMBTA56LT3 are not pin-compatible replacements. While both share the SOT-23 package and identical pinout (Pin 1 = Base, Pin 2 = Emitter, Pin 3 = Collector), they differ electrically: MMBTA55LT3 is rated for −60 V V_CEO, whereas MMBTA56LT3 is rated for −80 V. Substituting one for the other requires verification of voltage margin in the target circuit - MMBTA55LT3 must not be used where −80 V breakdown is required.

Does MMBTA55LT3 meet RoHS and REACH requirements?

Yes, MMBTA55LT3 is Pb-free and complies with EU RoHS Directive 2011/65/EU and REACH Regulation (EC) No. 1907/2006. The "G" suffix (e.g., MMBTA55LT3G) explicitly denotes Pb-free construction, but standard MMBTA55LT3 is also manufactured to the same Pb-free specification per onsemi documentation - confirmed in the "Pb−Free Packages are Available" feature statement and J-STD-609 classification.

What is the typical DC current gain (h_FE) of MMBTA55LT3 at −100 mA collector current?

The MMBTA55LT3 datasheet specifies h_FE ≥ 100 at −10 mA I_C, but does not guarantee minimum h_FE at −100 mA. Typical curves (Figure 5) show h_FE ≈ 70–90 at −100 mA and 25°C. For design-critical applications at high current, engineers should verify actual h_FE distribution in production lots or select a part with guaranteed h_FE spec at −100 mA, such as the NSS12201LT1G.

Can MMBTA55LT3 be used in linear amplifier configurations?

Yes, MMBTA55LT3 can operate in linear (active) mode with proper biasing - its f_T = 50 MHz and stable h_FE vs. temperature support low-noise preamplifier and emitter-follower stages. However, it lacks specified noise figure or linearity metrics (e.g., THD, IMR); for precision analog, dedicated low-noise transistors like BC847BPN are preferred. MMBTA55LT3 is best applied where moderate gain accuracy and bandwidth suffice.