onsemi TN4033A

Overview

TN4033A from Fairchild Semiconductor is a PNP general-purpose bipolar junction transistor designed for amplifier and switching applications up to 500 mA collector current and 70 V collector-emitter voltage, with DC current gain (hFE) of 100 at IC = 100 mA, VCE = 5.0 V, and VCE(sat) of 0.15 V at IC = 150 mA/IB = 15 mA - used in low-voltage power control circuits such as relay drivers and signal-level amplification stages.

For engineers reviewing the TN4033A datasheet, pinout, applications, or equivalent options, key selection considerations include its TO-226AE package, PNP polarity, 80 V VCEO rating, thermal resistance of 50 °C/W (junction-to-ambient), and suitability for discrete amplifier and medium-current switching designs requiring stable hFE across -40°C to +125°C.

Technical Context

The TN4033A operates as a silicon PNP BJT fabricated on Process 67, with negative-polarity voltage and current conventions. Its small-signal current gain (hfe) is 1.0–4.0 at IC = 50 mA/VCE = 10 V/f = 100 MHz, and it delivers pulsed hFE up to 300 at IC = 100 µA and 100 mA under specified bias conditions.

Switching performance is characterized by ton = 100 ns, tf = 50 ns, and ts = 350 ns at IC = 500 mA/IB1 = IB2 = 50 mA. Thermal design is supported by RθJA = 50 °C/W and PD = 1.0 W at TA = 25°C, derating linearly at 8.0 mW/°C above that temperature.

Key Specifications

Pinout & Package

Package: TO-226AE (also known as TO-92 variant), epoxy-molded, through-hole, 3-lead plastic package with flat side orientation marking emitter lead position. Standard lead form is straight, unclipped, with 0.300 g unit weight.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP general-purpose amplifier applications.

Compared with TN4033A, MPSA92 offers triple the voltage margin but sacrifices thermal performance and saturation voltage control, while BC557B provides superior hFE uniformity at low currents but cannot sustain 500 mA loads or 70 V bus operation.

Availability

TN4033A is available at Aetrix Electronics and suitable for relay drivers, DC motor controls, audio pre-amplifiers, and overvoltage protection circuits requiring stable component supply, consistent parametric performance, and long-term industrial lifecycle support.

Supply support for TN4033A 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and discrete components before its acquisition by ON Semiconductor in 2016; known for high-reliability bipolar transistors and rugged process technologies.

The TN4033A belongs to Fairchild's general-purpose PNP BJT product line, developed for cost-sensitive industrial and consumer applications requiring predictable gain, low saturation voltage, and wide temperature operation without integrated biasing.

FAQ

What is the maximum continuous collector current rating for the TN4033A?

The TN4033A has a maximum continuous collector current (IC) rating of 1.0 A at TA = 25°C, with derating applied above that ambient temperature. In practical switching applications, it is typically operated up to 500 mA to maintain reliability and thermal margin, as confirmed by its specified VCE(sat) and switching times at that current level. The TN4033A datasheet explicitly defines IC = 1.0 A as the absolute maximum rating under steady-state conditions.

Does the TN4033A support operation at elevated temperatures?

Yes, the TN4033A supports operation across a junction temperature range of -55°C to +150°C, with electrical characteristics guaranteed at -55°C, 25°C, and +125°C. At +125°C, hFE remains ≥70 at IC = 100 mA, and VCE(sat) increases only moderately to ≤0.35 V - enabling use in under-hood automotive modules and sealed industrial enclosures. The TN4033A thermal resistance values (RθJA = 50 °C/W, RθJC = 125 °C/W) further validate its high-temp capability.

What is the pin configuration of the TN4033A in the TO-226AE package?

When viewed with the flat side facing the user and leads pointing downward, the TN4033A TO-226AE package has pin 1 (Emitter) on the left, pin 2 (Base) in the center, and pin 3 (Collector) on the right - matching standard TO-92 orientation. This configuration is explicitly shown in Figure 1.0 of the official Fairchild TN4033A datasheet and verified in tape-and-reel packaging documentation (EOL code D26Z/D74Z). The TN4033A pinout is not interchangeable with NPN variants like PN2222 without circuit redesign.

How does the TN4033A compare to the BC557 in terms of DC current gain?

The TN4033A specifies hFE = 100 at IC = 100 mA and VCE = 5.0 V, with a minimum of 25 at IC = 1.0 A. In contrast, the BC557B guarantees hFE = 200–450 at IC = 2 mA, dropping to ~110 at 100 mA. Thus, the TN4033A delivers more consistent high-current gain and lower VCE(sat), while the BC557 excels in low-current, high-gain precision amplification. Both are valid, but the TN4033A is engineered for power switching where gain stability at 500 mA matters most.

Is the TN4033A suitable for switching 24 V inductive loads?

Yes, the TN4033A is suitable for switching 24 V inductive loads such as solenoids and small relays, given its VCEO = 80 V rating and built-in flyback energy handling capability. Its 350 ns storage time and 50 ns fall time enable clean turn-off, and the device should be paired with a reverse-biased diode across the load to clamp inductive kickback. The TN4033A's SOA curve and thermal specs confirm safe operation at 24 V/500 mA with minimal heatsinking, as validated in Fairchild's typical application curves.