# operational amplifiers

Discussion in 'Electronics Forum' started by Guest, Jun 8, 2007.

1. ### GuestGuest

I need help on the theory behind the voltages on an op-amps negative and positive terminal.

Why does the positive and negative terminals must have equal voltages?
2. ### GuestGuest

opamps

infinite gain is one of the ideal characterestics of op-amps.(so that it can amplify even the very weak signal.)
As the basic building block of opamp is differential amplifier, it amplifies the difference b/w the signals applied at the two terminals.
so.. the gain would be..
gain=v(out)/ v(id)=infinity
where v(out) is o/p voltage and v(id) is voltage difference b/w two terminals .
for the gain tobe infinite.. denominator should be zero..i.e., the difference b/w two terminal voltages should be zero..that's why the voltages at two terminals must be equal.. while treating for ideal case.
v(id)=V1-V2
vid=0=> V1=V2
3. ### GuestGuest

Two voltage power supplies having negative outputs with respect to common are combined to give positive as well as negative output with respect to common base . An operational preamplifier is always used as an inverter. The combination includes provision for programming by means of a voltage returned to common making the system compatible with Conventional remote control systems.