Problem 13.6 - Frequency Response (Bode Plot) for a First Order Circuit
*
* Use a steady-state sinusoidal source and an .AC sweep over the range
* of frequencies from 10 Hz to 1 MHz for the given RC circuit. Use
* PROBE to obtain separate graphs of the voltage amplitude in decibels
* (dB) and the voltage angle (phase).
*
* Follow the instructions of the problem statement to construct a
* straight line (approximate) Bode plot. Measure the error in decibels
* (dB) between the PROBE amplitude graph and the approximate graph.
* Also construct a straight line (approximate) phase plot and measure
* the errors. Check your results against textbook Table 13.2.
*
* ===> CHALLENGE PROBLEM! Modify the frequency sweep command (use an OCT
* sweep for the amplitude curve and a DEC sweep for the angle curve).
* Add a .PRINT command to obtain printed magnitude and phase values at
* the exact frequencies needed for accurate comparison with Table 13.2
* in the textbook.
*
* ===> CHALLENGE PROBLEM #2! In place of a paper and pencil construction of
* the approximate Bode plot, enter the expressions for the straight
* line approximations on the PROBE graphs of the amplitude and angle
* response. Use the two PROBE graph cursors to read the error values
* directly from the graph.
*
* AN EXTRA SPECIAL CHALLENGE! See if you can write the expression for
* the line with -20 dB/decade slope and use PROBE to plot it on the
* graph of the magnitude response. Likewise, write the expression for
* the -45 degrees/decade slope line that represents the approximate
* phase response, and plot it on the actual phase response curve.
*
.OPT NOPAGE NOBIAS ; This program is complete and ready to run.
; The exercise is in the graph work.
V1 1 0 AC 100
R1 1 2 1500
C1 2 0 106.1N
.AC DEC 10 10 1E6
.PROBE
.END
Prob 13.6, Part 2. Frequency Response (Bode Plot) for a First Order Circuit
*
* Obtain a printed output to check the dB error between the actual
* and the approximate curve against the textbook Table 13.2. Use
* an OCT sweep for this program run. (Values double every octave.)
*
.OPT NOBIAS NOPAGE
V1 1 0 AC 100
R1 1 2 1500
C1 2 0 106.1N
.AC OCT 1 62.5 ??? ; Enter a final value for the sweep.
.PRINT AC VDB(1) VP(1) VDB(2) VP(2)
.PROBE
.END
Prob 13.6, Part 3. Frequency Response (Bode Plot) for a First Order Circuit
*
* Obtain a printed output to check the phase error between the actual
* and the approximate curve against the textbook Table 13.2. Use a
* DEC sweep for this program run, with one point per decade.
*
.OPT NOBIAS NOPAGE
V1 1 0 AC 100
R1 1 2 1500
C1 2 0 106.1N
.AC DEC 1 10 ??? ; Enter a final value for the sweep.
.PRINT AC VDB(1) VP(1) VDB(2) VP(2)
.PROBE
.END