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Power supply for AMP in CAR


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MP and ANTE,
Maybe they use more transistors than is necessary in order to reduce the gamble of a high-gain transistor "hogging" the current. Also, extra transistors are probably cheaper than having many emitter resistors.
You didn't comment about my explanation for emitter resistors that I posted previously:



Ante,
Zapco either matched the paralleled transistors, or had good luck.
Think of emitter resistors as a form of negative feedback. When a high-gain transistor attempts to conduct a large collector current, then that current creates a voltage-drop across the emitter resistor, which reduces the base-emitter voltage and therefore reduces base-drive.
A transistor with less gain will attempt to conduct less current and therefore will have less base-drive reduction. So the gains of the transistors are equalized.
Without emitter resistors, when a high-gain transistor is paralleled with a low-gain one, then the high-gain transistor will conduct more current than the low-gain one, which results in unbalanced current sharing. Without balanced sharing, the high-gain transistor may exceed its maximum current and/or thermal rating and blow-up.
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closer than what you might think ante. What you have stated is approximately what I was saying but in a different way. I have not had much use for square wave inverters in the past.
Linear is quite different as I have found on my bench, though. And of course, the sinewave inverters are a little different because of this.

A comment about changing the transistors: Why would you do anything different? If the circuit has caused a break down in one transistor, I would be willing to believe the others have had a hard life as well. I always replace components as sets, too.

MP

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Sure, lots of devices use this array. As it stated in the pdf that I posted, it is for speed of transition. I do not understand where you think there is an argument....unless you mean you are arguing with the contents of the article that I posted.

MP

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