In the circuit of Fig. 1.27. Vi(t) and V0(t) are voltages (at time t) and R1 and R2 are resistors. There is also an ideal diode that acts as a short circuit when Vi, is positive and as an open circuit when vi is negative. We view Vi and V0 as the system input and output, respectively. Determine an input-output description of this system. Is this system linear? Is it time-varying or time-invariant? Is it causal? Explain your answers.
Explanation / Answer
a) When Vi(t) > 0, Vo(t) = Vi(t)*R2/(R1+R2), When Vi(t) < 0, Vo(t) = 0 b) The system is linear as output is directly proportional related to the input. It is time-varying as the output is dependent on time. It is causal because the output value is dependent on the input at the present value.