Please help, which of these two constant current sources is better?

太白金星

Please help, which of these two constant current sources is better? [Copy link]

Two constant current source designs, please tell me which one is better.
Two applications: one current is more than 20mA, and the other needs a maximum current of 1A. Thank you!

maychang

It is rather doubtful whether these two circuits can work properly.

The OP said that the maximum current is 1A, and the gate sampling resistor of the MOS tube uses 1 ohm. The voltage drop on this sampling resistor alone is 1V, so the 3.3V power supply voltage is only 2.3V. With a voltage of 2.3V, even the blue LED cannot light up.

maychang

In the circuit on the left, R4 is 10 kilo-ohms and R5 is 100 kilo-ohms. I don’t know what this means.

qwqwqw2088

The MOS tube may not be able to drive

木犯001号

Each has its pros and cons.

1nnocent

If the input and output are in phase, the one on the right is better.

1nnocent

It is better to add a voltage follower buffer to the left input. After adding the voltage follower, the two circuits feel similar.

Gen_X

As for the circuit itself, the second one is more accurate than the first one.

However, since R7 and R9 in the second circuit may be calculated incorrectly, the output may be problematic and the expected effect may not be achieved.