The problem with that is the current will vary between 0 to 20mA as the voltage is varied between 0 to 10V.
The original poster wanted 0 to 10V to be converted to
4mA to 20mA, hence the negative voltage to get 4mA when the input voltage is 0V.
It's important that the current never drops to zero because that's treated as an error on a current loop transmission system.
hi,
Thats a small change to make the circuit 4mA to 20mA.
Thanks for the link, but I have used 4-20mA for quite a time.