Is it a good idea to have those three amplifiers with LM741 Operational amplifier? Has anyone done this so far? I thought of this as this was a cheapest idea. The instrumentation amplifier costs about $6 but the quad LM741 costs like $2. I know that buying instrumentation amplifier would be most effcient. But does anyone see any huge disadvantage in this making of instrumentation amplifier with three LM741 op-amps?