onsemi NZT44H8

Overview

NZT44H8 from ON Semiconductor is an NPN power transistor designed for high-current linear and switching amplifier applications, featuring 60 V V_CEO, 8.0 A continuous collector current, and 1.5 W total device dissipation in SOT-223 package. It delivers DC current gain (h_FE) of 60 at I_C = 2 A and supports 50 MHz current gain–bandwidth product for medium-frequency amplification stages in audio and industrial power control circuits.

For engineers reviewing the NZT44H8 datasheet, pinout, applications, or equivalent options, key selection considerations include its SOT-223 thermal performance (R_θJA = 83.3 °C/W), V_CE(sat) ≤ 1.0 V at 8 A/0.4 A drive, and suitability for Class AB audio output stages, DC motor drivers, and linear voltage regulators requiring discrete high-current gain devices.

Technical Context

The NZT44H8 is a silicon NPN bipolar junction transistor fabricated using Fairchild's Process 4Q, optimized for speed and power handling in linear and switching modes. Its design emphasizes low saturation voltage and stable DC current gain across temperature, with guaranteed h_FE ≥ 40 at I_C = 4 A and V_CE = 1 V.

Thermal behavior is defined by R_θJC = 2.1 °C/W and R_θJA = 83.3 °C/W on standard FR-4 PCB land pattern, supporting operation from –55 °C to +150 °C junction temperature. The device exhibits f_T = 50 MHz under 500 mA/10 V conditions, confirming suitability for audio-frequency amplification and fast-switching regulator control.

Key Specifications

Pinout & Package

NZT44H8 is housed in a SOT-223-4L surface-mount package with four terminals: Collector (pin 1), Base (pin 2), Emitter (pin 3), and Collector tab (pin 4). The exposed collector tab serves as both electrical connection and primary thermal path to PCB copper.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN power amplifier applications.

Compared with MJD44H8 and ZTX448, NZT44H8 uniquely balances 60 V/8 A capability with SOT-223 manufacturability-offering best-in-class power density for medium-current linear and switching roles where TO-220 is too large and DPAK is incompatible with existing assembly lines.

Availability

NZT44H8 is available at Aetrix Electronics and suitable for audio amplifier output stages, DC motor drivers, linear voltage regulator pass elements, and switching regulator control transistors requiring stable component supply and consistent parametric performance across production lots.

Supply support for NZT44H8 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 (formerly Fairchild Semiconductor) is a global semiconductor manufacturer specializing in power management, analog, sensor, and discrete solutions for automotive, industrial, and consumer markets.

The NZT44H8 belongs to ON Semiconductor's legacy NPN power transistor family, originally developed for high-reliability linear amplification and switching applications where robustness, predictable gain, and thermal stability are critical.

FAQ

What is the maximum junction temperature specification for NZT44H8?

The NZT44H8 has a specified operating and storage junction temperature range of –55 °C to +150 °C. This 150 °C maximum junction temperature is used to derive all absolute maximum ratings, including V_CEO and I_C. Thermal design must ensure that actual junction temperature under operating conditions remains within this limit, especially given its SOT-223 package R_θJA of 83.3 °C/W.

Does NZT44H8 have a built-in base-emitter resistor or protection diode?

No, NZT44H8 is a standard three-terminal NPN bipolar junction transistor with no integrated base-emitter resistors or protection diodes. It requires external base current limiting and, in switching applications, may need a reverse-biased base-emitter clamp diode to prevent damage during inductive turn-off. The device's internal structure matches conventional discrete BJT topology as confirmed in the Fairchild D44H8/NZT44H8 datasheet Rev. 1.1.0.

Can NZT44H8 be used in parallel configurations for higher current handling?

NZT44H8 is not characterized for guaranteed current sharing in parallel configurations due to inherent h_FE and V_BE(on) variations across units. While possible with individual emitter resistors and matched devices, the datasheet does not specify matching tolerances or derating guidelines for paralleling. For >8 A applications, ON Semiconductor recommends evaluating alternative topologies such as MOSFET-based designs or dedicated multi-die packages instead of relying on parallel NZT44H8 units.

What is the recommended land pattern for NZT44H8 in PCB layout?

The official land pattern recommendation for NZT44H8 is SOT230P700X180-4BN, defined in the datasheet with specific dimensions: 7.30 mm × 6.70 mm overall outline, 3.25 mm × 1.90 mm pad for pin 1 (C), 1.90 mm × 1.90 mm pad for pin 2 (B), 3.25 mm × 1.90 mm pad for pin 3 (E), and a 6.10 mm × 2.30 mm thermal pad for pin 4 (C tab). Adequate copper area on the thermal pad is essential to achieve the rated R_θJA of 83.3 °C/W.

How does NZT44H8's f_T of 50 MHz impact its use in audio amplifier circuits?

NZT44H8's 50 MHz f_T ensures sufficient gain margin well above the 20 kHz audio band, enabling stable operation in Class AB output stages with feedback loop compensation. Measured at I_C = 500 mA and V_CE = 10 V, this f_T supports low-distortion amplification up to ~100 kHz, making it suitable for high-fidelity pre-driver and output transistor roles where phase shift and gain roll-off must be minimized across the audible spectrum.