As before, when you choose "(1) Sceptre" from the Main Menu. either by pressing "1" or by using the "F1" function key, you'll enter the Sceptre Module. The screen display will look as follows:

            Sceptre Module

            Filename [<Enter>=Quit]  ? _

For our second example, we'll analyze a single-stage feedback amplifier. This particular circuit was selected because it has been analyzed by other software, and the results are given in the literature for you to look at: See Pgs. 218-222 of Reference 4. Another reason for selecting this circuit is because it will give you valuable experience on how to parallel connect two different two-port networks.

We'll show you how to use the TWO code to represent a two-port device, the SRL element, and the other three output formats: S2, IR, and OR.

In response to the filename question above, type in "AMPS1" and then press <Enter>.

The circuit diagram for this amplifier is shown below, followed by the .CKT file listing.

CAP	AA	PA	3
IND	BB	SE	10
SRL	CC	SE	208	28
TWO	DD	S1	50
PAR	CC	DD
RES	DD	PA	300
CAP	EE	PA	3
IND	FF	SE	10
CAX	AA	FF
PRI	AA	S1	50
END
10	100	250	500	750	1000	1250	1500
.95	-2	7.35	174.6	.003	84.3	1.01	-1
.92	-11	7.15	168.0	.007	79.0	.99	-4
.87	-28	6.83	154.5	.015	69.2	.96	-10
.78	-54	6.28	135.0	.026	54.0	.90	-18
.69	-78	5.67	123.0	.033	41.4	.84	-26
.63	-09	5.04	113.0	.037	33.0	.79	-30
.60	-114	4.42	99.9	.038	29.3	.77	-33
.60	-127	3.88	87.0	.039	28.0	.76	-35

              
Carefully study the .CKT file listing shown above. In the fifth line above, the SRL and TWO are parallel connected using the PAR CC DD command. See Appendix B if this is not clear. Also, note that, after using the PAR CC DD command, that DD is again made available for use in the next line down  Now, the first eight lines describe the circuit from left to right. All these two-port networks are then cascaded in line 9 using the CAX AA FF command.

Having created a new two-port, AA, which represents the entire amplifier circuit, we now "finish up" the file. As when we created the FILTER file, we must specify the output format, issue an END command, specify the analysis frequencies, and, since this is an active circuit, and not passive one, as FILTER was, we must enter scattering parameter data for the TWO, the active two-port device.

The convention within Sceptre, in what has become standard format for s-data, thru out the industry, is shown below:


The scattering parameters S11, S21, S12, and S22 are entered, in that order, and in Mag/Ang form, where "M" is magnitude, as "A" is angle.

If you had two (or more) active devices, you would enter the s-data as follows:


After entering the filename as "AMPS1," (several lines up), Sceptre then asks:

            Analysis or Tweak (A/T) [<Enter>=Quit]  ? _

In response, type "A," press the <Enter> key, and then choose not to print by pressing <Enter> once again.

Note: At this point, you'll be asked "Print Logfile (Y/N) [<Enter>=No] ? _" Please press <Enter>.

If you choose the option to 'Print Logfile,' the data will be directed to 'Logfile.txt' within the \mwdata2 sub-directory, and to the screen. Right-click on 'Logfile.txt' to print it, and then DELETE the file; it will re-create when next needed.

Please please <Enter> to choose "N" in response to the above question.

A brief Analysis in progress message will flash on-screen, followed by data output to the screen. Your screen display should look similar to the following:

Sceptre Circuit Analysis on 07-18-2006 at 16:23:32

Filename:   AMPS1

Freq	S11 Mag/Ang	S21 Mag/Ang	S12 Mag/Ang	S22 Mag/Ang	S21(dB)  K  B1
10	0.075/   16.8	2.684/ 175.4	0.184/   -0.2	0.043/ 138.2	8.57  1.25  0.76
100	0.077/   10.9	2.665/ 163.0	0.182/ -15.5	0.080/ 103.2	8.52  1.26  0.77
250	0.095/     5.2	2.711/ 140.1	0.178/ -41.0	0.145/   78.4	8.66  1.23  0.77
500	0.218/    -6.0	2.954/ 100.4	0.168/ -83.7	0.191/   63.3	9.41  1.14  0.80
750	0.436/  -34.0	3.200/   58.7	0.146/-130.5	0.230/   83.4	10.10 1.11  0.86
1000	0.628/  -71.0	3.260/   11.7	0.119/-178.1	0.366/   83.4	10.26 1.10  0.88
1250	0.489/-108.6	3.528/  -51.7	0.104/ 125.0	0.364/   94.0	10.95 1.08  0.95
1500	0.632/  -66.6	1.999/-144.1	0.047/   42.3	0.872/   89.4	6.02   1.12  0.27

Task Completed

Follow the on-screen instruction to "Press any Key" to return to the opening prompt. It would be a good idea for you to now run AMPS2, it adds stability circles to the display, and is the second of four different Sceptre output formats.

The only difference between the AMPS1 and the AMP2 .CKT files, both of which are in the \mwdata2\ sub-directory, is line 10. In AMPS1, you see PRI AA S1 50, while in AMPS2 its been changed to PRI AA S2 50.

If you do choose to run AMPS2, here is what will happen: The amplifier circuit will first be analyzed as it was above, and data output to the screen, again as above, then, at the bottom  of the screen, you'll see "Press any Key." This is a pause, because the 25-line DOS window is full, and without it, you would not see  the first half of the output data. When you do "Press any Key," stability circle data will be output to the screen.

There are two other output data formats: they are IR and OR. The two amplifier data files in the \mwdata2 sub-directory  containing them are named, respectively, AMPIR and AMPOR.

Let's try the IR print option to see what the output format looks like, O.K.? First, return to the opening prompt, where you'll be asked:

            Sceptre Module

            Filename [<Enter>=Quit]  ? _

Enter the filename as "AMPIR" and then press <Enter>. Choose the analysis option, and choose not to print, or create a Logfile. Here is what the IR output format looks like:


Sceptre Circuit Analysis on 07-18-2006 at 16:40:10