5.1-9 a zero-order-hold circuit (fig. p5.1-9) is often used to reconstruct a signal g(t) from its samples. (a) find the unit impulse response of this circuit. (b) find and sketch the transfer function h( f ). (c) show that when a sampled signal g(t) is applied at the input of this circuit, the output is a staircase approximation of g(t). the sampling interval is ts.