MPSA42 NPN Transistor: Pinout, Datasheet and Replacement

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The MPSA42 is a common NPN transistor that has been widely employed in high-voltage switching and amplification applications. It's a more advanced type of amplifier with enhanced over-voltage and voltage break-down safety. When compared to traditional type amplifiers such as the LM741 OP-AMP, it is extremely adequate with a low collector current amplifier. It's constructed of silicon and comes in a typical TO-92 package that's easy to find. What’s more, the MPSA42 has a 300volts emitter to collector voltage.

ON Semiconductor MPSA42 technical specifications, attributes, parameters and parts with similar specifications to ON Semiconductor MPSA42.

• Type: NPN bipolar transistor

• The gain in DC: 40.

• Collector- emitter voltage: 300V

• Collector -base voltage: 300V

• The base voltage of the emitter: 6V.

• Transition frequency: 50MHz

• Maximum operating junction temperature: +150C0

• Collector base capacitance: 3pF

• The forward current transfer ratio must be at least 25.

• Continuous collector current: 500mA

• Maximum collector power dissipation: 0.625W

• Thermal resistance from junction to ambient: 200C0/W

• Current cutoff for the collector: 0.1A

• High voltage switching

• In Audio amplifiers

• Low current motor drive circuits

• High power LED diver circuits

• Speed control stepper motor circuits

• Various temperature control circuits

• Communication circuits

• Analog to digital converters

You can replace MPSA42 with KST42, MMBTA42, and PZTA42.

2N3904, 2N3906, S9014, BC547, SS8550, SS8050, 2N2369, 2N3055

The MPSA42 is an NPN transistor with a high voltage. A transistor can be used as a switch or an amplifier, but due to its low gain value of 30, this transistor is commonly used only for switching. Because the MPSA42 can turn on or off high voltage loads (up to 300V), it is frequently utilized for heavy loads or loads with a high peak voltage. Also, because the IC's collector current is 500mA (0.5A), you won't be able to drive loads that require a lot of currents. Because it has a 6V Base-Emitter voltage, it can be easily controlled with microcontrollers or other digital devices.

Therefore, if you're seeking an NPN transistor that can switch high voltages while maintaining a reasonable current flow, the MPSA42 transistor could be the one for you.

In the following circuit, the NPN transistor will be employed as a switch in a motor control circuit. Because the MPSA42 transistor is often used for high voltage switching, we'll show you how to utilize it to turn on and off a high voltage dc motor (48V). The motor is connected to this NPN transistor as shown in the diagram below.

MPSA42 Circuit

A 1K resistor is used to apply 5V dc voltages to the base pin. The formula RB= VBE / IB is used to compute the value of this resistor. Where we know that if VBE is 5V and IB is 500mA, RB is 1K. When 5Votls is applied to the base pin, current flows and the transistor connects to the ground, causing the motor to turn on. When the base pin receives zero volts, no current flows, the transistor does not connect to the ground, and the motor does not turn on.

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