Problem 10.2 - Complex Impedance as a Function of Frequency
*
* The circuit for this problem is from textbook Chap. 10, Problem 14.
*
* Determine the input impedance at three frequencies using the .AC
* sweep function. Print out the magnitude and phase of voltage V(1).
* Note that, because the input current has amplitude 1 and zero angle,
* the complex voltage V(1) is numerically equal to the circuit input
* impedance.
*
* ===> CHALLENGE PROBLEM! The results from the program run indicate that
* the circuit is primarily capacitive at the low frequency, primarily
* resistive at the middle frequency, and primarily inductive at the
* highest frequency. As a PSpice experiment to explore this effect:
* 1. Substitute a SIN source for the ac current source in the
* program. Use a peak amplitude of 1, a frequency equal to
* one of the frequencies of the ac sweep of the original
* program, and an angle of 90ø to simulate the cosine wave.
* 2. Use the .TRAN command with the SIN source (instead of .AC sweep,
* which is used only with a steady-state ac sinusoidal source).
* You will need a .TRAN analysis period equal to approximately five
* periods of the cosine wave at each of the frequencies you use.
* 3. There will be a start-up transient in each case unless you enter
* the initial conditions. Since the forcing function is a current
* source, the initial current is obvious "by inspection." Use the
* relationship between capacitance voltage and current to calculate
* the initial capacitance voltage.
* NOTE: The transient voltages are very large in this problem when
* the initial conditions are not specified. You may be interested
* in trying to predict the t=0 transient voltage and verify it with
* a PSpice experiment.
* 4. Obtain a PROBE graph showing the source current, the voltage
* V(1), and the voltages across the inductance and the capacitance.
* a. The graph at the low frequency will show that the input
* voltage lags the current by almost 90ø. The capacitance
* voltage is almost identical to the input voltage, indicating
* that the circuit is predominantly capacitive. The inductance
* voltage is very small, and almost negligible.
* b. At the middle frequency, the input voltage is in phase
* with the source current, indicating that the circuit is a
* primarily resistive circuit. The capacitance voltage lags
* and the inductance voltage leads the current by 90ø.
* c. At the highest frequency the inductance voltage
* dominates. The input voltage and the inductance voltage lead
* the current by almost 90ø. The capacitance voltage is
* negligibly small.
*
.OPT NOPAGE NUMDGT=5 NOBIAS ; Use this statement with Version 4.03 or
; later. For earlier versions delete NOBIAS.
IS1 0 1 AC 1
RS1 1 0 1E12 ; Resistance in parallel with the current
; source to provide a dc path to ground.
R1 1 2 1
C1 3 0 1U
L1 2 3 1U
.AC DEC 1 ??????? ??????? ; Enter the frequencies in hertz. Use
; six significant figures.
.PRINT AC ; Complete the .PRINT statement for the
; input voltage amplitude and angle.
; You may also print the real part and
; the imaginary part of the complex
; voltage. When the input current has
; amplitude=1 and angle=0, the real
; and imaginary parts of the input
; voltage are equal to the real and
; imaginary parts of the complex input
; impedance.
.END
* Problem 10.2, Part 2. CHALLENGE PROBLEM! Complex Impedance at 15915.5 Hz
*
* Follow the instructions above to obtain PROBE graphs showing the
* voltage and current relationships for the R, L, and C of the
* circuit for frequencies below, at, and above the series resonant
* frequency of the circuit.
*