Hai khâu nối tiếp cách nhau bởi khâu lấy mẫu có hàm truyền G(z) là

\(G\left. z \right.=\frac{C\left. z \right.}{R\left. z \right.}={G}_{1}(z){G}_{2}(z)\)

\(G\left. z \right.=\frac{C\left. z \right.}{R\left. z \right.}={G}_{1}{G}_{2}(z)\)

\({G}_{k}\left. z \right.=\frac{C\left. z \right.}{R\left. z \right.}=\frac{G(z)}{1+GH(z)}\)

\({G}_{k}\left. z \right.=\frac{C\left. z \right.}{R\left. z \right.}=\frac{G(z)}{1+G(z)}\)