Hi, the transistor/Ampops in the schematic are not the final ones. These components are there only for simulation. The Electronics Workbench has a big library but is a little old. The power transistor has to be symmetric so I have been search the web and I found: NPN 2n5631 PNP 2n6031 16A 140V 200W NPN 2n3772 PNP 2n6609 16A 140 V 150W NPN 2n3055 PNP MJ2955 15A 90V 114W For current sense and voltage reference generator ampops you can use tl081 if you build a regulated power supply of 15V 0V -15V, “LM7815 LM7915” this is because the opa445AP cost 8.40euros “Portugal Price”. For the 2n2369 sorry, my mistake….. The positive current sense is well connected, but in the schematic you cant see that. The wires are very close, sorry. For the negative one I need a negative output. If you invert the inputs the ampop will not give you – X.XX V because -31.74V – (-34V) = 2.26V and not -2.26V. Thanks audioguru.