The Ideal Op-amp

 Ideal

1.       Voltage gain - infinite                                                      need to use negative feedback

2.       Input resistance – infinite                                                 no input to current to op amp

3.       Output resistance – zero                                                 no voltage signal los at output

4.       Bandwidth – infinite                                                        works on DC and AC up to any frequency

Actual

1.       Voltage Gain (Av) - 200,000                                         need to use negative feedback                

2.       Input resistance  - 1 MΩ                                                input current to Op-Amp will be pA

3.       Output resistance - 75Ω                                                 very little output signal loss

4.       Bandwidth up to - 1MHz                                               works on DC and AC up to 1 MHz

Bandwidth

Range of frequencies over which the circuit functions

Feedback

·         A connection between output and input in a circuit or system

·         Most commonly negative feedback to tend to reduce the effect of the input and maintain a stable state

Limitation

Output voltage can never exceed power supply voltage

Basically a small voltage from a circuit controlling a large voltage