函數(shù)信號(hào)發(fā)生器設(shè)計(jì)外文資料及翻譯-在線瀏覽
2025-03-05 10:36本頁(yè)面
【正文】 sfy this condition. Then, because circuit ponents and, more importantly, transistors change characteristics (drift) with ahe, temperature, voltage, etc., it is clear that if the entire oscillator is left to itself, in a very short time will bee either less or larger than unity. In the former case the oscillation simply stops, and in the latter case we are back to the point of requiring nonlinearity to limit the amplitude. An oscillator in which the loop gain is exactly unity is an abstraction pletely unrealizable in practice. It is accordingly necessary, in the adjustment of a practical oscillator, always to arrange to have somewhat larger (say 5 percent) than unity in order to ensure that, with incidental variations in transistor and circuit parameters, shall not fall below unity. While the first two principles stated above must be satisfied on purely theoretical grounds, we may add a third general principle dictated by practical considerations, .:In every practical oscillator the loop gain is slightly larger than unity, and the amplitude of the oscillations is limited by the onset lf nonlinearity. Root locus of the threepole transfer function in the splane. The poles without feedback () are ,and,whereas the poles after feedback is added are ,and .2. Triangle/square generation shows a function generator that simultaneously produces a linear triangular wave and a square wave using two opamps. Integratoris driven from the output ofwhere is wired as a voltage parator that’s driven from the output of via voltage divider . The squarewave output of switches alternately between positive and negative saturation levels.Suppose, initially, that the output of is positive, and that the output of has just switched to positive saturation. The inverting input of is at virtual ground, so a current equals. Becauseandare in series, and are equal. Yet, in order to maintain a constant current through a capacitor, the voltage across that capacitor must change linearly at a constant rate. A linear voltage ramp therefore appears across,causing the output ofto start
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