Question 2 (40 marks) With reference to Fig. 2, (a) write a formula (symbols only) for the Thévenin equivalent voltage and resistance of the subcircuit to the left of nodes 2

and 0 (i.e. Vs, R3 and R4), wwwww (b) calculate the numerical value of the voltage e3 at node 3 at time 1 ms and (c) calculate the numerical value of the voltage e3 at time 1 s, when R1 = R3 = (1000 + y) 22, R2 = R4 = (2000+5) 2, C1 = (1000 + E) nF, and C1 is initially discharged (i.e. the voltage e2 at node 2 is zero at t = 0). Vs is a piecewise-linear voltage source in which Vs = 0 for t < 100 us, and Vs = 1 V for tz 100 μs. www Vs Vth www. Rth www. e3(1ms) e3(1s) R3 R4 R1 Figure 2 0 R2 OPAMP C1 3 30% 40% 20% [+]