Diodes Incorporated FMMT551TA

Overview

FMMT551TA from Diodes Incorporated is a PNP silicon planar medium-power transistor in SOT23 package, rated for -60 V V_CEO, -1 A continuous collector current, and 500 mW power dissipation at 25°C ambient. It serves as a general-purpose switching and linear amplification device in low-voltage DC-DC converter bias circuits, LED driver current sinks, and industrial sensor interface stages.

For engineers reviewing the FMMT551TA datasheet, FMMT551TA pinout, FMMT551TA application, or FMMT551TA equivalent, key selection criteria include verified V_CEO(sus) = -60 V, h_FE = 50–150 at IC = -150 mA, f_T = 150 MHz, V_CE(sat) ≤ -0.35 V at IC/IB = 10, and SOT23 terminal mapping with emitter (pin 1), base (pin 2), collector (pin 3).

Technical Context

This PNP bipolar junction transistor operates in active, saturation, and cutoff regions with defined safe operating area up to 100 V and 2 A pulsed. Its h_FE exhibits dual-range specification: min 50 at IC = -150 mA/V_CE = -10 V and min 10 at IC = -1 A/V_CE = -10 V, supporting both small-signal gain stability and high-current switching fidelity.

Transition frequency f_T = 150 MHz at IC = -50 mA/V_CE = -10 V/f = 100 MHz confirms suitability for audio-frequency amplification and fast-switching applications up to ~10 MHz practical bandwidth. Output capacitance C_obo = 25 pF at V_CB = -10 V enables predictable turn-off timing in inductive load drivers.

Key Specifications

Pinout & Package

SOT23 plastic surface-mount package with gull-wing leads; standardized JEDEC TO-236AB outline, 1.3 mm × 2.9 mm footprint, 1.1 mm height, and 0.95 mm lead pitch. Thermal pad not present; power dissipation relies on PCB copper thermal mass.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP medium-power transistor applications.

Compared with ZTX653 and MMBT5551, FMMT551TA offers balanced trade-offs: verified -1 A capability with moderate h_FE spread, making it optimal for cost-sensitive industrial switching where 150–500 mA operation dominates and thermal budget is constrained.

Availability

FMMT551TA is available at Aetrix Electronics and suitable for industrial sensor interfaces, LED current sink drivers, DC-DC converter bias circuits, and relay coil drivers requiring stable component supply with full traceability and no minimum order quantity.

Supply support for FMMT551TA 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

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, headquartered in Plano, Texas, with design centers across Asia and manufacturing in China, Taiwan, and Malaysia.

FMMT551TA belongs to the FMMT series of medium-power SOT23 transistors engineered for industrial-grade reliability in space-constrained switching and amplification applications up to +150°C junction temperature.

FAQ

What is the maximum allowable junction temperature for FMMT551TA?

The absolute maximum junction temperature is +200°C, with storage temperature also rated from -55°C to +200°C. Derating begins at T_amb > 25°C per the thermal resistance θ_JA = 250°C/W (typical for SOT23 on 1-in² 1-oz copper), requiring PCB thermal design to maintain T_J ≤ 150°C for long-term reliability.

Does FMMT551TA have built-in ESD protection?

No, FMMT551TA does not integrate ESD protection diodes. Its base-emitter junction has inherent ESD sensitivity per IEC 61000-4-2 Level 2 (±4 kV contact); handling requires grounded wrist straps and ionized air, and PCB layout should include local TVS or RC filtering if exposed to user-accessible ports.

Can FMMT551TA replace BC857 in existing designs?

Yes, with verification: both are SOT23 PNP transistors with V_CEO = -60 V and I_C = -100 mA (BC857) vs. -1 A (FMMT551TA). FMMT551TA's higher current rating and lower V_CE(sat) allow direct substitution in low-current roles, but base resistor values may require adjustment due to h_FE differences (BC857 h_FE = 125–630 vs. FMMT551TA's 50–150).

Is SPICE model support available for FMMT551TA?

Yes - Diodes Incorporated provides verified SPICE parameter data upon request, including Gummel-Poon model coefficients extracted from measured DC and AC characteristics. The model supports accurate simulation of V_CE(sat), f_T, and safe operating area boundaries in tools like LTspice and PSpice.