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Ohms law contains three variable terms. You have only mentioned two of them.if the resistance increases,current decreases according to the Ohms law & it's a law so
how current source can be constant?
tks
sid
No, not really. It will control the "V".it means to keep I constant these devices controll's the R ?
To be picky, the transistor doesn't adjust the gain which a constant for any particular transistor. The transistor gain causes the transistor to adjust its current to maintain a constant 0.7V across Rset, thus generating a constant current.If it helps, here's an actual constant-current source I've built that works (I use it to test LEDs using a 9-volt battery):
**broken link removed**
The transistor adjusts its gain, based on the voltage drop sensed across Rset (which increases as current increases) to keep the current constant. It works very well, within a certain voltage range.
It should be noted that the feedback is such as to make the output impedance of the constant current appear very high (infinity for the ideal source). Thus any changes in the output voltage due to a change in load resistance have no effect on the output current.A constant current source will adjust its output voltage to maintain constant current (possibly by adjusting its own internal resistance). Whatever it needs to do to keep the output current constant.
There will always be a limit to how much adjustment range a constant current source can provide depending on its design.
To be picky, the transistor doesn't adjust the gain which a constant for any particular transistor. The transistor gain causes the transistor to adjust its current to maintain a constant 0.7V across Rset, thus generating a constant current.
Hmm... no, not really.so to keep the I constant V-out is controlled in a certain range by Manipulating internal resistance?