I was trying to design a driver of a proportional valve. My driver has ±10VDC input and ±100mA output (Load: 200 ohm, 0.5 H, Series RL) I have two supplies which are 28±4VDC and -28±4VDC. I applied this circuit and simulated. I take ±100mA when i applied ±32VDC to opamps supplies however i took ±90mA for ±28VDC and ±75mA for ±24VDC. It was fixed to 100mA when i applied bigger supplies than ±32VDC. Also there is some problem about load, the output current should be independent from load resistor but values bigger than 200 ohm, the current was influenced. I have included the circuit.
I investigated some proportional valve models and i realised that they can give almost 3A. Do you know that how that circuits can give those currents? My circuit is limited at some values for some reasons but i couldn't find it.
This is a commercial circuit example for proportional valve: http://agsotomasyon.com.tr/content/ags-pv02-2-kanal-oransal-valf-kontrol-karti