I'm trying to design a bidirectional current source for the purpose of measuring very small (0.0001 Ohm) resistances. I've come across this circuit: I can see that the transistors are there to 'boost' the current but I don't understand the purpose of the 1K resistors and the capacitor. I also don't follow how I can increase the current rating of this pump to 1A. I've simulated the circuit in LTSpice and it works very well at 100mA but when I try to source or sink 1A I only get 850mA out. Any suggestions on increasing the current sourcing/sinking ability of the above circuit to 1A or any other suggestions for such a pump?