Electronics > Beginners
circuit of precision 1A current source, how thus this circuit work?
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aidilismadi:
thank you so much :) the mosfet part is a little complicated but i'll try to understand :)
rstofer:
The simple way to think of the MOSFET is as a water valve.  More water flows when the valve is open and in the case of the MOSFET, the water valve is the gate voltage.  As the gate voltage goes higher, the valve is more open and more water/current flows.  When the gate voltage goes down, the valve is more closed and the water/current flow decreases.

There are many details like Vgs and the various gate capacitances, in fact, there is an entire datasheet full of numbers.  In the end, the MOSFET is nothing more than a voltage controlled water valve with some details around the edges.
aidilismadi:
thank you so much :) for the explanation on mosfet
RandallMcRee:

That MOSFET explanation does not cover the fact that a MOSFET has polarity. An N type wants a positive gate voltage and a P type wants negative with respect to source.

Its very important in your circuit to have the correct MOSFET both polarity and current rating.

Do you know that a MOSFET (or transistor) will simply self-destruct at high current if not heat-sinked?
Audioguru:
The datasheet for the TL082 opamp shows that it has two opamps in it. The unused opamp might be interfering with the opamp in it that you are using. Use a single opamp instead.
The datasheet for the TL082 opamp also shows that its Common Mode Input Voltage Range is 4V more positive than its negative supply voltage so its inputs DO NOT WORK if their voltage is less than +4V in your circuit. The TL08x opamps have the Phase Inversion Problem then its output will go as high as it can if an input voltage is within a few volts from 0V in your circuit. It needs an additional negative supply of -3V or more.

Instead you could use an opamp that has inputs that work as low as +1V in your circuit. 
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