Chapter 2: Difference between revisions
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=Ideal Op Amp Characteristics= | ==Ideal Op Amp Characteristics== | ||
*[[Chapter_1#Amplifier_Models | Infinite input impedance]] | *[[Chapter_1#Amplifier_Models | Infinite input impedance]] | ||
*Infinite open-loop gain for the differential signal | *Infinite open-loop gain for the differential signal | ||
| Line 8: | Line 8: | ||
**To allow for infinite gain regardless of the frequency? Instantaneous feedback? | **To allow for infinite gain regardless of the frequency? Instantaneous feedback? | ||
=Op Amp Nodal Analysis= | ==Op Amp Nodal Analysis== | ||
*[[Chapter_1#Amplifier_Models | No current flows into the + or - terminals]] | *[[Chapter_1#Amplifier_Models | No current flows into the + or - terminals]] | ||
*If negative feedback is present (and no positive feedback), then <math>V_+ = V_-\,</math> | *If negative feedback is present (and no positive feedback), then <math>V_+ = V_-\,</math> | ||
*Write nodal equations at <math>V_+\,</math> and <math>V_-\,</math>, but not at <math>V_o\,</math> | *Write nodal equations at <math>V_+\,</math> and <math>V_-\,</math>, but not at <math>V_o\,</math> | ||
**There is a voltage source inside the op amp. Writing a nodal equation at a voltage source adds an extra equation and an extra variable. You gain no ground. | **There is a voltage source inside the op amp. Writing a nodal equation at a voltage source adds an extra equation and an extra variable. You gain no ground. | ||
Revision as of 14:14, 11 January 2010
Ideal Op Amp Characteristics
- Infinite input impedance
- Infinite open-loop gain for the differential signal
- Zero gain for the common mode signal
- You can easily change an differential amplifier into a common-mode amplifier by grounding one of the inputs
- Zero output impedance
- Infinite bandwidth
- To allow for infinite gain regardless of the frequency? Instantaneous feedback?
Op Amp Nodal Analysis
- No current flows into the + or - terminals
- If negative feedback is present (and no positive feedback), then
- Write nodal equations at and , but not at
- There is a voltage source inside the op amp. Writing a nodal equation at a voltage source adds an extra equation and an extra variable. You gain no ground.