Diodes Incorporated FMMT455TA

Overview

FMMT455TA from Diodes Incorporated is a high-voltage, medium-current NPN silicon planar transistor in SOT-23 package, rated for 140 V_CEO, 1 A continuous collector current, and 500 mW power dissipation. It delivers h_FE = 100–300 at I_C = 150 mA / 1 A and f_T = 100 MHz, enabling use in DC-DC converter switching stages and industrial relay drivers.

For engineers reviewing the FMMT455TA datasheet, FMMT455TA pinout, FMMT455TA application, or FMMT455TA equivalent, key selection criteria include V_CEO ≥ 140 V, I_C ≥ 1 A, h_FE stability across 150 mA–1 A, switching speed (t_r/t_f ≤ 300/900 ns), and SOT-23 thermal performance under pulsed load conditions.

Technical Context

This device operates as a general-purpose high-voltage NPN switch with guaranteed V_CEO(sus) = 140 V under sustained load and V_CBO = 160 V for collector-base isolation. Its h_FE exhibits dual-tier specification: 100–300 at I_C = 150 mA (linear amplification) and 10–300 at I_C = 1 A (switching saturation), supporting both analog gain and digital on/off control.

Transition frequency f_T = 100 MHz at I_C = 50 mA / V_CE = 10 V confirms RF-capable switching up to ~10–20 MHz practical duty-cycle operation. Output capacitance C_obo = 15 pF at V_CB = 10 V enables predictable turn-off energy calculation in inductive load circuits.

Key Specifications

Pinout & Package

SOT-23 plastic surface-mount package with gull-wing leads; standard pin assignment confirmed per Diodes Incorporated FMMT455 series marking diagram and mechanical drawing 3-110.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage NPN switching applications.

Compared with ZXTN25050DFH and MMBT4401, FMMT455TA uniquely balances 140 V blocking, 1 A DC current, and 100 MHz f_T in SOT-23-making it irreplaceable in 48–100 V industrial switching where both voltage margin and switching speed matter.

Availability

FMMT455TA is available at Aetrix Electronics and suitable for industrial relay drivers, DC-DC converter switches, LED string controllers, and high-voltage sensor interfaces requiring stable component supply across extended temperature ranges (−55°C to +150°C).

Supply support for FMMT455TA 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 Taiwan and China.

FMMT455TA belongs to the FMMT high-voltage transistor family, engineered specifically for robust switching in industrial control, power conversion, and automotive body electronics where reliability under voltage stress is critical.

FAQ

What is the maximum safe operating voltage for FMMT455TA in continuous DC mode?

The absolute maximum collector-emitter voltage is V_CEO = 140 V with base open. For reliable long-term operation, design should limit steady-state V_CE to ≤112 V (80% of rating) to accommodate transients and temperature derating. Pulse operation up to 140 V is permitted only under specified duty cycle ≤2% and pulse width ≤300 µs.

Does FMMT455TA require a base resistor when driven by a 3.3 V microcontroller GPIO?

Yes. With h_FE ≥100 at I_C = 150 mA, a minimum base current of 1.5 mA is needed. Using a 2.2 kΩ resistor between 3.3 V GPIO and base yields ~1.1 mA after V_BE(on) ≈ 0.75 V drop-sufficient for light loads. For full 1 A saturation, reduce resistance to ≤470 Ω to deliver ≥5 mA base current.

Can FMMT455TA replace BC847 in existing SOT-23 designs?

No-BC847 has V_CEO = 45 V and I_C = 100 mA, making it unsuitable for FMMT455TA's 140 V/1 A use cases. Pinout matches (E-B-C), but substituting without circuit redesign risks catastrophic failure under voltage stress or thermal overload. Only consider if original design operates below 30 V and 100 mA with ample safety margin.

Is SPICE model availability confirmed for FMMT455TA?

Yes-Diodes Incorporated explicitly states "Spice parameter data is available upon request for this device" in the official datasheet (Issue 3, February 1996). Models include accurate junction capacitance, forward beta roll-off, and saturation characteristics validated against measured f_T, V_CE(sat), and C_obo values.