Wide range constant current supply

[Greg]

Does anyone have any ideas to build a simple constant current supply
that can be adjustable from 10uA to 30mA? The input voltage can be
from 24-40VDC. The typical LM317 does not regulate at low currents,
and it seems that devices that can regulate at low currents, like the
LM234, can not put out more than about 10mA.

Thanks,
Greg

 

[The Al Bundy]

Does anyone have any ideas to build a simple constant current supply
that can be adjustable from 10uA to 30mA? The input voltage can be
from 24-40VDC. The typical LM317 does not regulate at low currents,
and it seems that devices that can regulate at low currents, like the
LM234, can not put out more than about 10mA.

Thanks,
Greg

What about a transconductance amplifier? These should be able to deliver
such low currents.

Al

 

[John Popelish]

Does anyone have any ideas to build a simple constant current supply
that can be adjustable from 10uA to 30mA? The input voltage can be
from 24-40VDC. The typical LM317 does not regulate at low currents,
and it seems that devices that can regulate at low currents, like the
LM234, can not put out more than about 10mA.

Thanks,
Greg

Many opamps can deliver current in this range, and an opamp with a
small fet current booster (2N7000, BS170, etc.) works well in this
range. What frequency response do you need?

 

[Greg]

Many opamps can deliver current in this range, and an opamp with a
small fet current booster (2N7000, BS170, etc.) works well in this
range. What frequency response do you need?

Good idea. Frequency response will not be an issue, since the circuit
will be operating in a DC mode.


Greg

 

[Greg]

Thanks for the replys. I got a circuit that works great. It took 1
quad op amp, 6 resistors, one capacitor, and one pot.

Greg

 

[Baphomet]

Thanks for the replys. I got a circuit that works great. It took 1
quad op amp, 6 resistors, one capacitor, and one pot.

Greg


[email protected] (Greg) wrote in message

How about posting the circuit?