ABSTRACT
Operational amplifiers nearly always use negative feedback, obtained by feeding back some, or all, of the output to the inverting (−) input (as shown in Figure 18.5 later). The feedback produces an output voltage that opposes the one from which it is taken. This reduces the new output of the amplifier and the resulting closed-loop gain A is then less than the open-loop gain Ao . However, as a result, a wider range of voltages can be applied to the input for amplification. As long as Ao >> A, negative feedback gives:
(i) a constant and predictable voltage gain A, (ii) reduced distortion of the output, and (iii) better frequency response.
