Hello mates,
i'm trying to make a 20mA/10V driver (signal output from a device, to drive VFDs and other industrial equipment):
Requirements.
Source topology (active loop), supplied by external 24V
20mA @ 2.5Vin or 10V @ 2.5Vin, user selectable. I wish was only a single jumper bridge.
In voltage mode, current limited, anything from 20 to 100mA is good enough
In current mode, drive up to 600ohms loads (12V output)
Frequency up to 1KHz
The 2.5V input will come from STM32F1 DAC (12bit), using a 3V reference
I wish the opamp will run at 5V (or 3.3V), I would like to some general purpose, low drift, nothing fancy.
First I tought of using a howland current with external transistor but, the opamp output should be higher than 5V to drive an NPN as source
Them I tried to feedback the opamp from a differential current sense resistor (49.9Ohms).
Using ltspice the circuit has a strange behavior (high gain, I suppose) when connected to the opamp, but not with a 2.5V signal source.
I would like to learn more about analog electronics for sure.