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”