2SA1943 is a silicon PNP power transistor consist of triple diffuse technology. 2SA1943 comes in robust TO220-IS package with an inbuilt large heat sink as the back plain of the 2SA1943 transistor. It is recommended to use 2SA1943 in power amplifier applications with suitable NPN transistor. Pinout and the physical appearance of the 2SA1943 transistor is given below image.


Lets identify some of the key features of the 2SA1943 PNP transistor.

  • High collector to emitter voltage of 230V
  • Maximum 1.5A of base saturation current
  • 150W high power junction power dissipation
  • Maxim of 150 degrees of Celsius junction working temperature
  • Maximum recommended amplifier power stage foe 2SA1943 is 100W

You can see although the 2SA1943 transistor can dissipate 150W of power it is recommended to use for maximum of 100W amplifiers. This is because the performance of the 2SA1943 transistor can be reduced due to long term high load applications even when it is used within the given limits of the datasheet of the  2SA1943 transistor. You can see a simple 100W amplifier circuit using 2SA1943 in below give circuit diagram.

In this circuit we have used 2SC5200 NPN transistor with our key component 2SA1943 PNP transistor. Also you can see we have used a small NPN transistor called 2SC2383 as a pre signal amplifier this is because almost every audio input devices such as mp3 players, DVD players, Mobile phones only give an audio output in mV range. This mV range signa is not enough to bias the base of the power transistors ( 2SA1943 & 2SC5200) so the job of the small signal NPN transistor is to amplify the audio input signal to high enough voltage to power transistors to amplify. Also we have used 10k potentiometer to control the input signal gain by doing so we can control the volume of the amplifier. We can use two of these circuit to built a stereo amplifier for better audio quality. One key disadvantage of this amplifier is it does not have overload or short circuit protection so make sure never to short the speaker lines together that will destroy the power transistors. Other than that this is a very good circuit to a beginner in electronics.

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