Question

Need Pspice simulations

Please do the computer simulations before or after the lab (it's recommended that you finish it before) 1- Set up the following R-C circuits. VCC 741 VEE R > 22062 C20.1uF Measure and make plots of vin(t) and ve(t) on the same graph as well measure and tabulate phase shift between vin(t) and vc(t) for the given conditions RC 2RC ORC RC 10 RC **Tips: Pick a value for R and C, then change o according to the conditions*** Briefly explain and comment your results

Answer 1

Answers:

1. I used LTSpice to build and simulate the circuit. The circuit diagram is given below for your reference:

V2 U1 R1 5V 220 V1 C1 V3 SINE(0.15 7243 0 0 0 0) AC.15 0 5V .tran 0.010.00001

2. Recall that in RC circuit of this kind the phase shift is given by

Theta = tan^-1(WRC), where W = angular frequency in radians/sec

Now the five different cases:

a) W=1/RC

This theoretically gives a phase shift of Theta = tan^-1(WRC) = tan^-1(RC/RC) =tan^-1(1) = 45 degrees

The result of simulations are shown below. Trace in green shown Vin. Trace in blue is the waveform across the capacitor. Note that the angular difference between the two traces is 45 degrees as predicted.

(Note that for simulation we need to input the frequency in Hz and not in rad/sec. In this case the freq. in Hz is W/(2*pi), that is 7234Hz)

150mV 120mV 90mV 60mV 30mV OmV 30mV -60mV -90mV -120mV -150mV 0.0ms 0.2ms 0.4ms

b) W=1/2RC

Therefore Theta = tan-1(1/2) = 26.6 degrees

V(n004) 150mV 120mV 90mV- 60mV 30mV 0mV -30mV -60mV -90mV- 120mV 150mV 0.9ms 1.0ms 1.1ms 1.2ms 1.3ms

c) W = 1/(10RC)

Theta = tan^-1(1/10) = 5.7 degrees

V(n004) 200mV- 160mV 120mV 80mV 40mV OmV 40mV 80mV 120mV 160mV -200mV 240mV 0.9ms 1.2ms 1.5ms 0.0ms 0.3ms 0.6ms

d) W = 2/RC

Therefore Theta = tan^-1(2) = 63.5 degree

150mV 120mV 90mV- 60mV 30mV OmV 30mV -60mV 90mV -120mV 150mV 0.18ms 0.27ms 0.36ms

e) W = 10/RC

Therefore Theta = tan^-1(10) = 84.3 degrees

V(n004) 200mV 160mV 120mV 80mV 40mV 0mV -40mV -80mV 120mV 160mV -200mV 240mV Ous

Some observations:

So through these five simulations we notice that the phase shift increases as W (angular freq.) increases. This is in line with what the phase shift formula Theta = tan^-1(WRC) predicted.

Also note that the amplitude of the output voltage is given Vo = Vi/(1+jWRC). As W is increased, Vo reduces. This is also clear in the simulation results shown above. This makes this circuit a low-pass filter.

Hope this helps.