Problem 11.7 - Phasor Voltage as a Function of Frequency
*
* The circuit for this problem is from textbook Chap. 11, Problem 39.
*
* Determine the amplitude and angle (magnitude and phase) of V(3)
* as functions of frequency over the range 10 Hz to 1 MHz.
* Use PROBE to display a graph of VM(3). The frequency at which the
* voltage is reduced to .707 times its low-frequency (or dc) value is
* called the half-power frequency or -3dB frequency or the critical
* frequency of the circuit. (It also has several other names, all of
* which imply the same end result to those who use the special names.)
* To determine the critical frequency, select "Add_trace" and enter
* the expression (dc volt)/SQRT(2), where "dc volt" is the numerical
* value of the voltage at the lowest frequency on the graph. A line
* will be drawn across the graph, intersecting the magnitude curve at
* the critical frequency.
*
* You can also use the cursor function to find the half-power point
* on the frequency response curve. Move one cursor out on the curve
* with the other cursor remaining "parked" at the lowest frequency
* on the graph. When the moving cursor is at an amplitude that is
* .707 times the amplitude of the parked cursor, you have located the
* half-power frequency. Read the value from the cursor window.
*
* Another method of accomplishing the same goal is to "Add_trace" the
* constant 135 on the graph of VP(3). This will draw a line on the
* graph at 135 degrees and will intersect the phase curve at the
* frequency where the phase shift is 45 degrees from the angle at the
* lowest frequency on the graph. The critical frequency determined
* from the phase plot and from the magnitude plot should agree.
*
* You may also use the PROBE cursor function to locate the point on
* the phase curve where the phase angle is 135 degrees.
*
.OPT NOPAGE NOBIAS
V1 1 0 AC 1
E1 3 0 ??? ??? 1E10 ; Enter the control voltage +/- nodes.
R1 ; Enter the resistance device nodes
R2 ; and values for the circuit.
R3
R4
RL
C1 2 3 22.1N
.AC ; Complete the .AC sweep command.
.PROBE
.END