1. Operational amplifier

2. Definition The operational amplifier is a linear device for general purpose that features the managing signals from f = 0 Hz to a frequency defined by the manufacturer. The O.A. is an amplifier of high gain directly connected that feeds on positive and negative sources.

3. The ideal Operational Amplifier is characterized for 1) Input resistor. It tends to infinite. 2) Output resistor. It tends to zero. 3) Tension profit of opened bow. It tends to infinite. 4) Bandwidth. It tends to infinite. 5) vo = 0 when v+ = v-

4. Internal structure  The operational amplifier has four blocks. The first is the differential that can have a darlington entry or can use multiple FET and a constant current source. After, there is a linear amplifier stage of high gain, usually another differential amplifier. If the existing voltage of c.c. at the output of the amplifier of high gain is not zero volts when v1 = v2 = 0 V, it is used a scroller circuit of level as a "cascodo" amplifier. The last stage is an output amplifier, usually one of complementary symmetry.  The operational amplifier has four blocks. The first is the differential amplifier that can have a darlington entry or can use multiple FET and a constant current source. After, there is a linear amplifier stage of high gain, usually another differential amplifier. If the existing voltage of c.c. at the output of the amplifier of high gain is not zero volts when v1 = v2 = 0 V, it is used a scroller circuit of level as a "cascodo" amplifier. The last stage is an output amplifier, usually one of complementary symmetry.

5. Three basic manners of operation 1) Inverter mode: 2) Non-inverter mode: 3) Open-loop mode:

6. Some examples