Q. Show Noise and Stability of operational amplifier?
Noise
This refers to the small, rapidly varying, random spurious signals generated by all electronic circuits. Noise places a limit on the smallness of signals that can be used. The subject of random signals and noise belongs to a branch of electrical engineering known as communication theory.
Stability
The amplifier is said to be stable when it performs its function reliably under all normal operating conditions. By definition, a system is stable if its response to an excitation that decays to zero with time also decays to zero. Instability can come about in various ways, and it is a very common difficulty, which must be prevented. In almost all cases, op-amp circuits can be classified as feedback circuits. Feedback of an improper kind can lead to instability or oscillation of an op-amp circuit. In general, instability occurs when there is excessive phase shift in the
op amp and feedback loop, so that negative feedback is changed to positive feedback. The frequency response of an op amp is usually designed to roll off smoothly at 20 dB decade, as mentioned earlier. This type of frequency response ensures stability for the more common op-amp circuits.