neazoi
Advanced Member level 6
Hi,
I want to power an AM7910 IC from the USB port of the computer. The +5v is straight forward, but the chip requires also -5V 15-25mA max (depended on the version).
So the question is how to derive this amount of current for the negative voltage, out of the USB port?
I like to do it discrete, so please do not suggest me ICs dedicated for the purpose.
Two possible circuits I have found are the next, the first is an oscillator and a negative charge pump and the second uses a multiplier instead. I think a multiplier is better, because it will allow me to regulate the voltage afterwards with a 7905 and obtain a stable voltage for the IC.
But I wonder, how about replacing the 555 with a simple 2 transistors multivibrator?
The point is, how much current could I get out of such a circuit and what are the things that define the current? (collector resistors, frequency of oscillator?)
Thank you
I want to power an AM7910 IC from the USB port of the computer. The +5v is straight forward, but the chip requires also -5V 15-25mA max (depended on the version).
So the question is how to derive this amount of current for the negative voltage, out of the USB port?
I like to do it discrete, so please do not suggest me ICs dedicated for the purpose.
Two possible circuits I have found are the next, the first is an oscillator and a negative charge pump and the second uses a multiplier instead. I think a multiplier is better, because it will allow me to regulate the voltage afterwards with a 7905 and obtain a stable voltage for the IC.
But I wonder, how about replacing the 555 with a simple 2 transistors multivibrator?
The point is, how much current could I get out of such a circuit and what are the things that define the current? (collector resistors, frequency of oscillator?)
Thank you
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