The MPSA92 transistor is a widely used high-voltage PNP device. Its solid electrical characteristics, compact TO-92 package, and compatibility with various control circuits make it a practical choice for anyone working with voltage levels that exceed the capabilities of standard low-voltage transistors. This article will discuss the MPSA92 transistor in detail, covering its key parameters, uses, and important considerations.

Catalog

MPSA92 Transistor Overview

The MPSA92 is a high-voltage PNP bipolar junction transistor designed for applications requiring reliable switching or amplification at voltages up to 300 V. Housed in a compact TO-92 package, it offers moderate current handling (up to 500 mA) and stable performance in power supply drivers, relay interfaces, and other high-voltage control circuits. Its structure makes it suitable for designs where conventional low-voltage transistors cannot safely operate.

With a typical gain range of 25–40 and a transition frequency around 50 MHz, the MPSA92 provides dependable switching speed without excessive complexity. Designers must consider its modest power dissipation of ~625 mW and ensure proper biasing, especially when used near its voltage limits. This makes it ideal for lightweight, space-efficient circuits that demand high voltage but moderate current.

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MPSA92 Alternatives & Equivalents

MPSA92 Transistor Specifications

MPSA92 Transistor Features

High-voltage PNP bipolar transistor

300 V Collector-Emitter breakdown voltage

Can handle up to 500 mA collector current

Low saturation voltage (≈ 500 mV)

Moderate DC gain (hFE 25–40)

50 MHz transition frequency for stable switching

625 mW maximum power dissipation

Wide operating temperature range (−55°C to +150°C)

Compact TO-92 through-hole package

Suitable for high-voltage switching and amplifier applications

Low leakage current (ICBO ≈ 250 nA)

Durable long-body package option for various PCB layouts

Using MPSA92 Transistor

The circuit demonstrates how the MPSA92 high-voltage PNP transistor can be used to drive a Nixie tube using a low-voltage control signal. A 160 V supply powers the tube, while the MPSA92 switches this high voltage on and off safely. The transistor’s base is biased through a 360 kΩ resistor, limiting current and protecting the device from excessive base drive.

A BS108 N-channel MOSFET controls the base of the MPSA92. When the MOSFET receives a square-wave signal, it pulls the base of the MPSA92 low, turning it on and allowing current to flow through the Nixie tube. When the MOSFET turns off, the MPSA92 stops conduction, extinguishing the display. The 80 kΩ resistor in series with the tube sets the proper operating current, ensuring stable illumination.

MPSA92 Transistor Applications

High-Voltage Switching

The MPSA92 is commonly used in circuits that must switch high-voltage loads while being controlled by low-voltage signals. Its 300 V rating allows it to operate safely in environments where typical low-voltage transistors would fail. You can often use it to switch power rails, activate high-voltage displays, or control circuits requiring isolation between the control logic and high-voltage section.

Nixie Tube Drivers

Nixie tubes require voltages of 150–200 V, making the MPSA92 ideal for driving their anodes or cathodes. The transistor can handle the high-voltage demands while being controlled by microcontrollers or MOSFETs at low voltages. This ensures the tube illuminates properly while maintaining electrical safety and preventing excessive current through the display.

High-Voltage Signal Amplifiers

In some analog applications, the MPSA92 functions as a small-signal amplifier for high-voltage circuits. Its ability to withstand large voltage swings makes it suitable for audio or control signal processing in specialized equipment. Although not intended for high-gain precision amplification, it serves reliably in circuits that prioritize voltage handling over performance.

Relay and Solenoid Drivers

The MPSA92 can be used to control relays or solenoids that operate at higher voltages than low-voltage transistors can support. By placing the transistor between the high-voltage source and the coil, the device enables safe switching via low-power control signals. This allows microcontrollers or timing circuits to activate high-voltage electromechanical components without risk of damage.

Power Supply and Inverter Circuits

In high-voltage power supply designs, the MPSA92 is often used in start-up circuits, voltage sensing, and small-signal control sections. Its tolerance for high collector-emitter voltage makes it useful for powering control blocks in switch-mode supplies or inverters. It helps manage startup sequences or provide stable biasing in circuits where voltage spikes commonly occur.

MPSA92 CAD Models

Comparison: MPSA92 vs. MPSA42

MPSA92 Transistor Mechanical Drawing

MPSA92 Advantages and Limitations

MPSA92 Advantages

Supports high voltages up to 300 V, making it ideal for HV switching.

Works well in circuits that require low-current control of high-voltage loads.

Compact TO-92 package suitable for small designs.

Reliable performance with moderate switching speed (50 MHz).

Compatible with many Nixie tube and display driver circuits.

Low leakage current ensures stable operation in sensitive designs.

Often used as the PNP complement to MPSA42, enabling push-pull HV stages.

MPSA92 Limitations

Obsolete part, making sourcing more difficult.

Relatively low current gain (hFE) compared to modern transistors.

Limited power dissipation (625 mW) restricts high-current applications.

TO-92 package offers minimal heat dissipation, requiring careful thermal design.

Not suitable for precision amplification due to modest gain characteristics.

Requires careful handling in high-voltage circuits to ensure safe operation.