模拟信号U(t)的波形图如图所示，它的时间域描述形式是：
A.u(t) = 2(1-e-10t)?l(t) B.u(t) = 2(1-e-0.1t)?l(t) C.u(t) = [2(1-e-10t)-2]?l(t) D.u(t) = 2(1-e-10t)?l(t)-2?l(t-2)正确答案D
模拟信号U(t)的波形图如图所示，它的时间域描述形式是：
A.u(t) = 2(1-e-10t)?l(t) B.u(t) = 2(1-e-0.1t)?l(t) C.u(t) = [2(1-e-10t)-2]?l(t) D.u(t) = 2(1-e-10t)?l(t)-2?l(t-2)正确答案D
