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Homemade electronics Stuff old and new
DC Powerload, electronic load, fets, opamp

This DC powerload is homemade with 10 big N-FET
It has two current ranges 0-6.5A and 0-75A

This design (low rds on, low source resistance) is specially made for low voltage, but very high currents)
It is much better to use higher RDS on, and higher value source resistors, incase your needed voltage, and current range alow it
This way the opamp will be able to drive the fets easier, more stable, and much less voltage to current gain in the system.

It can be set to be a constant-current load or a constant-resistor load.
A simple modification could add a Constant-Watt load possibility.

I have made this to test my homemade powersupply, to check if overload protection,
and shortcircuit protection works.

The schematic is so simple: just compare the voltage over a sense resistor with a variable voltage
the output of the opamp goes to the 10 gates, remember to have a 10-100 Ohm resistor in series with each gate,
This will prevent oscillation..

If the variable voltage is comming from the input loading voltage, you have a resistor type of load.
If the variable voltage is from a zener regulated voltage, you have a constant current load.
If the variable voltage is comming from the input loading voltage, but is inverted ! you have a constant watt type of load.

Here is a fast handdrawn schematic, due to all the requests.

OZ2CPU 1993