Operational Amplifier

Ope Amp

1. Differential amplifier - amplifies difference between two signals.
2. Can amplify very small voltage signals to a useful level.
3. Typically an 8 lead IC.
4. Op Amps can require one power supply (single supply) or a positive and a negative power supply (dual supply)

Feedback

1. Degree of amplification can be controlled using feed back
2. Applied inverting or non inverting input

A=1+(R1/Rn)

Basic Op Amp Function

1. If (inverting input) > (non-inverting input) output saturates towards -Vss
2. If (inverting input) < (non-inverting input) output saturates towards +Vss
3. Without feedback maximum saturation occurs with the slightest difference between inputs.
4. Ideal op-amp has infinite impedance on the inputs, infinite gain, and zero resistance on output.
5. In real life gain is limited to voltage present at +Vss/-Vss
6. For practical purposes there is no current flow from the inputs to the outputs. The input voltage serves only as a reference to control the output.
7. Degree of amplification can be controlled using feedback.
8. Feedback can be applied to the inverting or non-inverting input.
9. Feedback applied to the inverting input is more common and is called negative feedback.
10. Gain (A) = 1 + (Rf/Rin)