October 2002
Intermediate to advanced
432 pages
9h 20m
English
The opamp can serve as a square-wave oscillator by adding positive feedback with R1 and R3 and replacing Ry with a capacitor Co, as shown in Fig. 12.2. The frequency of the operation can be computed on the basis of the following derivation. With positive feedback, the circuit is unstable and the output voltage is either Vop or –Vom, that is, the positive or negative limit. The limits are close to VDD or VSS. These voltage values are applied to the input through the positive feedback network such that the plus input terminal is either at
Equation 12.11
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or
Equation 12.12