Hello Everyone,
As I am reading the book of Op Amp for Everyone, chapter feedback theory. I come across this paragraph that I could not understand well:
Stability is determined by the loop gain, and when Aβ = –1 = |1| ∠–180° instability or oscillation occurs. If the magnitude of the gain exceeds one, it is usually reduced to one by circuit nonlinearities, so oscillation generally results for situations where the gain magnitude exceeds one. Consider oscillator design, which depends on nonlinearities to decrease the gain magnitude; if the engineer designed for a gain magnitude of one at nominal circuit conditions, the gain magnitude would fall below one under worst case circuit conditions causing oscillation to cease
so my confusions is that how can the oscillation happens (bold writing) when the gain Magnitude greater than 1 an also gain magnitude under 1!!???
I am sure that oscillations happens when Aβ = –1 = |1| ∠–180°, because Vout/Vin=A/(1+AB), since AB would be -1, which create infinite gain
Op Amp for Everyone
As I am reading the book of Op Amp for Everyone, chapter feedback theory. I come across this paragraph that I could not understand well:
Stability is determined by the loop gain, and when Aβ = –1 = |1| ∠–180° instability or oscillation occurs. If the magnitude of the gain exceeds one, it is usually reduced to one by circuit nonlinearities, so oscillation generally results for situations where the gain magnitude exceeds one. Consider oscillator design, which depends on nonlinearities to decrease the gain magnitude; if the engineer designed for a gain magnitude of one at nominal circuit conditions, the gain magnitude would fall below one under worst case circuit conditions causing oscillation to cease
so my confusions is that how can the oscillation happens (bold writing) when the gain Magnitude greater than 1 an also gain magnitude under 1!!???
I am sure that oscillations happens when Aβ = –1 = |1| ∠–180°, because Vout/Vin=A/(1+AB), since AB would be -1, which create infinite gain
Op Amp for Everyone