函數(shù)信號發(fā)生器設(shè)計外文資料及翻譯-全文預(yù)覽
【正文】 n in the active devices associated with the amplifier. Such a nonlinearity bees more marked as the amplitude of oscillation increases. This onset of nonlinearity to limit the amplitude of oscillation is an essential feature of the operation of all practical oscillators, as the following considerations will show: The condition does not give a range of acceptable values of , but rather a single and precise value. Now suppose that initially it were even possible to satisfy 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 an
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