onsemi FZT790A

Overview

FZT790A from onsemi is a PNP low-saturation bipolar junction transistor optimized for high-current switching in power management circuits, featuring V_CE(sat) = −0.25 V at I_C = −500 mA / I_B = −5.0 mA, h_FE ≥ 200 at I_C = −1.0 A, and −40 V V_CEO rating - deployed in DC-DC converter output stages and motor driver H-bridge high-side switches.

For engineers reviewing the FZT790A datasheet, pinout, applications, or equivalent options, key selection criteria include verified low V_CE(sat) under 2 A load, SOT-223 thermal performance (R_JA = 62.5 °C/W), RoHS-compliant Pb-free packaging, and guaranteed h_FE ≥ 150 at I_C = −2.0 A.

Technical Context

This PNP transistor uses epitaxial base construction to achieve low saturation voltage and high current gain across wide operating ranges. Its design supports continuous collector currents up to −3 A with stable h_FE down to −2.0 A and maintains safe operation from −55 °C to +150 °C junction temperature.

The device exhibits f_T = 100 MHz at I_C = −50 mA, enabling use in medium-frequency switching applications. Thermal derating is defined at 16 mW/°C above 25 °C ambient, consistent with its SOT-223 footprint and FR-4 PCB layout requirements.

Key Specifications

Pinout & Package

SOT-223 (Case 318H) package with exposed collector tab for thermal enhancement and mechanical mounting. Standard 4-pin configuration with collector connected to tab and pins 1–4 as marked.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ZXT790A and MJD2955T4G, the FZT790A delivers optimal balance of low saturation voltage, SOT-223 thermal integration, and 40 V system compatibility - making it preferred for compact, thermally constrained 24 V industrial switchers where drive simplicity and conduction loss are prioritized.

Availability

FZT790A is available at Aetrix Electronics and suitable for DC-DC converters, motor drivers, linear regulators, and industrial PLC outputs requiring stable component supply and long-term manufacturability.

Supply support for FZT790A 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 FZT790A belongs to onsemi's high-performance discrete transistor portfolio, engineered specifically for high-current, low-loss switching in space-constrained power conversion and control systems.

FAQ

What is the maximum continuous collector current rating for the FZT790A?

The FZT790A has a maximum continuous collector current (I_C) rating of −3 A at T_A = 25 °C. This rating assumes proper PCB thermal management per the datasheet's FR-4 layout guidelines. At elevated ambient temperatures, derating applies at 16 mW/°C above 25 °C, limiting usable current in high-temperature environments. The FZT790A maintains functional integrity up to 150 °C junction temperature.

Does the FZT790A require a heatsink in typical SOT-223 applications?

The FZT790A does not require an external heatsink when operated within its 2 W total power dissipation limit and mounted on a 76 mm × 114 mm FR-4 PCB with minimum land pattern, as specified in the thermal characteristics. Its R_JA = 62.5 °C/W enables self-cooled operation at ≤1.5 A continuous load in 25 °C ambient. For sustained 2–3 A operation or elevated ambient conditions, enhanced copper pour or thermal vias are recommended - but no discrete heatsink is needed for standard SOT-223 implementation.

What is the guaranteed DC current gain (h_FE) of the FZT790A at 2 A collector current?

The FZT790A guarantees h_FE ≥ 150 at V_CE = −2.0 V and I_C = −2.0 A, per the Electrical Characteristics table. This minimum gain ensures predictable base drive requirements in high-current switching applications. Measured h_FE typically exceeds 180 under those conditions, but design margins should be based on the 150 minimum to ensure robustness across process and temperature variation.

Can the FZT790A be used as a direct replacement for the older FZT788B in existing designs?

The FZT790A is not a direct replacement for the FZT788B due to differences in saturation voltage and gain profile: the FZT790A offers lower V_CE(sat) (−0.25 V vs. −0.35 V at −500 mA) and higher h_FE (≥200 vs. ≥100 at −1 A), but shares identical SOT-223 pinout and package dimensions. Layout compatibility is maintained, though base resistor values may need adjustment to optimize switching speed and avoid overdrive. System validation is recommended before drop-in substitution.

Is the FZT790A suitable for switching inductive loads such as relays or solenoids?

Yes, the FZT790A is suitable for switching inductive loads, supported by its −50 V V_CBO and −5 V V_EBO ratings, which provide margin against flyback voltage spikes. When used in such applications, a reverse-biased flyback diode must be placed across the load to clamp inductive kickback. The FZT790A's −40 V V_CEO rating ensures safe operation with 24 V systems and typical transient overshoot, provided the diode is correctly implemented and layout minimizes parasitic inductance.