Determine the transfer function V_{o}(s)/V_{i}(s) of the circuit shown in Figure 6.4.6.
The impedance of a capacitor is 1/Cs. Thus, the transfer function of the circuit is found from (6.4.2) with Z_{i}(s)=R\ {\mathrm{and}}\ Z_{f}(s)=1/C s. It is
{\frac{V_{o}(s)}{V_{i}(s)}}=-{\frac{Z_{f}(s)}{Z_{i}(s)}}=-{\frac{1}{R C s}}Thus in the time domain, the circuit model is
v_{o}=-{\frac{1}{R C}}\int_{\mathbf{0}}^{t}v_{i}\,d t (1)
Thus the circuit integrates the input voltage, reverses its sign, and divides it by RC. It is called an op-amp integrator, and is used in many devices for computing, signal generation, and control, some of which will be analyzed in later chapters.