The differentiator analyzed in Example 6.4.3 is susceptible to high-frequency noise. In practice, this problem is often solved by using a redesigned differentiator, such as the one shown in Figure 6.4.8. We will analyze its performance in Chapter 9 when we study the response of systems to sinusoidal inputs. Derive its transfer function.
Using the op-amp equation (6.4.2), we have
Vi(s)Vo(s)≈−Zi(s)Zf(s) (6.4.2)
Vi(s)Vo(s)=−Zi(s)Zf(s)where Zi(s)=R1+1/CsandZf(s)=R. The circuit’s transfer function is
Vi(s)Vo(s)=−Zi(s)Zf(s)=−R1Cs+1RCs (1)