Transfer functions of continuous-time systems
Problem 1: Consider the following system:
Let R1=40Ω,R2=20Ω,L=10mH,C=1μF. The input is vin the output is vout. Give both transfer function and state space representation for the system.
Solution
Given circuit is a second-order linear system due to presence of one inductor (L) and one capacitor (C).
Given transfer function H(s) is given by the ratio over Laplace domain:
H(s)=Vin(s)Vout(s)
Given that the impedance of the inductor Zl=sL and the impedance of the capacitor Zc=sC1, the total impedance of the circuit is given by:
Ztotal=sL1+sC1
Using voltage divider rule, the transfer function is given by:
H(s)=Vin(s)Vout(s)=sL1+sC1sC1