op amp

why do we use dual power supply in op amps ????? :roll:

Because of combination of NPN and PNP transistors at the input difference amplifier of any Op-Amp. Refer to Analog Devices OP-184 datasheet. This fact can be made out easily

Dual supply is used to bias the inetrnal differential amplifier's transistors in active region. Some op-amps have internal bisaing resistors which make them go in active region with single supply. One such op-amp is LM324. OP AMPS in inverting mode, instead of grounding non-onverting terminal, you have to connect it to a potential divider network haivng equal resistors say 5K or 10k. This will set the reference point at Vcc/2 and output voltage will swing from 0 to Vcc/2 to Vcc.