Why is the power consumption high when the operating voltage is low in the transistor constant current circuit?

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Why is the power consumption high when the operating voltage is low in the transistor constant current circuit? [Copy link]

I don't quite understand. If you draw a circle in the picture, please ask for help from the big guys

maychang

The so-called "working voltage" refers to the voltage across the resistor (load resistor) connected to the transistor collector. The "working voltage" plus the voltage between the transistor collector and emitter plus the voltage across the emitter resistor Re is equal to the power supply voltage. If the load resistance decreases, due to the constant current, the voltage across the load resistor decreases, while the voltage across Re remains unchanged (the current remains unchanged), the voltage across the transistor collector-emitter must increase, and thus the transistor power consumption increases (the transistor power consumption is approximately equal to the collector-emitter voltage multiplied by the constant current, that is, the collector current).

PCB我不会

maychang posted on 2018-10-31 16:30 The so-called "working voltage" refers to the voltage across the resistor (load resistor) connected to the collector of the transistor. "Working voltage" plus the collector of the transistor - ...

I always think that the load voltage is very small, and the selected input voltage should also be very small, so the power consumption of the transistor should not be very large. After reading the explanation of the big brother, I feel that I think too much. Thank you