onsemi PZTA92

Overview

PZTA92 from ON Semiconductor is a PNP bipolar junction transistor (BJT) designed for high-voltage amplifier and switching applications, featuring −300 V collector-emitter breakdown voltage (V_(BR)CEO), −500 mA continuous collector current (I_C), and 1000 mW power dissipation in SOT-223 package. It operates across −55 °C to +150 °C and delivers DC current gain (h_FE) of 40–250 at −10 mA I_C, suited for flyback driver stages in industrial power supplies.

For engineers reviewing the PZTA92 datasheet, pinout, applications, or equivalent options, key selection considerations include its high-voltage PNP capability, SOT-223 thermal performance (R_θJA = 125 °C/W), saturation voltage (V_CE(sat) = −0.5 V at −20 mA), and compatibility with high-side switching topologies requiring robust avalanche-rated transistors.

Technical Context

The PZTA92 employs a planar epitaxial base structure optimized for high-voltage blocking and stable gain under pulsed conditions. Its −300 V V_CEO and V_CBO ratings enable use in off-line switch-mode power supply snubber circuits and relay drivers where sustained reverse-biased collector-base stress occurs.

Thermal design leverages the SOT-223 package's exposed collector tab for direct PCB heat sinking, supporting 1 W dissipation with proper copper area. Electrical characteristics are specified at T_A = 25 °C with pulse testing (≤300 μs, ≤2% duty cycle) to ensure reliable operation in transient-heavy applications like CRT horizontal deflection or ignition coil drivers.

Key Specifications

Pinout & Package

SOT-223 4-lead plastic package with exposed collector tab (pin 3 and pin 4 internally connected to collector); thermally enhanced for surface-mount mounting on FR-4 PCBs with ≥76 mm × 114 mm copper area.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP high-voltage amplifier applications.

Compared with MJD2955G and PN2907A, the PZTA92 uniquely balances −300 V blocking, 1 W dissipation in SMT form, and stable gain-making it the only viable SOT-223 PNP option for 230 VAC-derived power stage drivers without compromising footprint or thermal margin.

Availability

PZTA92 is available at Aetrix Electronics and suitable for industrial power supplies, high-side relay interfaces, linear regulator pass elements, and ignition coil drivers requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for PZTA92 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 is a global semiconductor manufacturer specializing in power management, analog, sensor, and discrete solutions for automotive, industrial, and cloud infrastructure markets.

The PZTA92 belongs to ON Semiconductor's legacy high-voltage bipolar transistor portfolio-originally developed by Fairchild Semiconductor-to address demanding off-line and high-reliability switching applications with robust thermal and voltage margins.

FAQ

What is the maximum safe operating voltage for PZTA92 in continuous DC applications?

The PZTA92 has an absolute maximum V_CEO rating of −300 V at T_A = 25 °C. For continuous DC operation, derating is required above 25 °C ambient; the device remains safe up to −300 V only when junction temperature stays ≤150 °C. In practice, design margins should limit steady-state V_CE to ≤−240 V to accommodate transients and temperature effects. The PZTA92 datasheet specifies this rating under pulsed test conditions (≤300 μs), so DC use demands careful thermal analysis to avoid exceeding T_J(max).

Can PZTA92 replace MMBTA92 in existing SOT-23 designs?

No-PZTA92 cannot directly replace MMBTA92 due to incompatible packages (SOT-223 vs. SOT-23), different pinouts, and distinct thermal/power capabilities. While both share the same electrical family, the PZTA92's SOT-223 footprint requires PCB redesign, and its higher power dissipation (1000 mW vs. 350 mW) necessitates larger copper areas. The PZTA92 also has different thermal resistance (125 °C/W vs. 357 °C/W), altering temperature rise calculations. Use PZTA92 only in new designs targeting higher power or better thermal performance-not as a drop-in substitute for MMBTA92.

What is the recommended base resistor value for switching PZTA92 at 20 mA collector current?

To achieve −20 mA I_C with typical h_FE = 100, a base current of −200 μA is required. With V_BE(sat) = −0.9 V and a 3.3 V MCU GPIO driving the base through a resistor to emitter, R_B = (3.3 V − 0.9 V) / 0.0002 A = 12 kΩ. A standard 10 kΩ resistor ensures sufficient overdrive while limiting base power dissipation. This value assumes room-temperature operation; at −40 °C, h_FE drops, so 6.8 kΩ may be preferred for guaranteed saturation across the full −55 °C to +150 °C range of the PZTA92.

Does PZTA92 support avalanche energy rating for inductive switching?

The PZTA92 datasheet does not specify single-pulse avalanche energy (E_AS) or repetitive avalanche ratings. Its −300 V V_(BR)CEO is a DC breakdown parameter measured with I_C = −1 mA, not an avalanche-safe operating limit. For inductive load switching (e.g., relays or ignition coils), external clamping-such as a reverse-biased TVS diode across C–E-is mandatory to absorb stored energy and prevent secondary breakdown. Relying on inherent avalanche capability of the PZTA92 is unsafe and unsupported by ON Semiconductor characterization data.

How does the SOT-223 package of PZTA92 improve thermal performance versus TO-92 alternatives?

The SOT-223 package of the PZTA92 provides significantly lower thermal resistance (R_θJA = 125 °C/W) compared to TO-92 equivalents like PN2907A (~200 °C/W), due to its exposed collector tab soldered directly to PCB copper. With a 76 mm × 114 mm FR-4 board and minimum land pattern, the PZTA92 sustains 1 W dissipation at T_A = 25 °C-nearly 3× the power handling of TO-92 devices without heatsinks. This enables compact, fanless industrial designs where space and reliability are critical, and eliminates mechanical mounting constraints associated with through-hole TO-92 packages.