Changes

At this point, your BJT amplifier circuit is ready for an overall Network Analysis Test. Replace Q1 (the standard BFG193 model) with NP1 (RF BJT model of BFG193). Place the "IN" marker right after the source resistor, and place the "OUT" marker at the load resistor. Replace the AC voltage source with a piece of wire as shown in the opposite figure.  remove the source and load resistors and run a Network Analysis Test of the true amplifier circuit independent of the source and load. The opposite figure shows this circuit with the source and load sections removed.  {{Note|For a two-port Network Analysis Test, you should remove the voltage source, source resistance and load resistance from your circuit.}}    Run a network analysis of this circuit with start and stop frequencies set at 500MHz and 1500MHz and with a linear frequency step size of 10MHz. Plot the S-[[parameters]] on an amplitude-only Cartesian graph. The figure below shows the results for s11, s21, s12 and s22 [[parameters]].

[[File:RF135.png|thumb|450px|The RF BJT Amplifier with S-parameter RF BJT model for AC network analysis.]]Keep in mind that the results you obtained so far included the source and load resistors. They represent the S-[[parameters]] of your overall network. For the purpose of our analysis and comparison with the results of the next part, it is instructive to remove the source and load resistors and run a Network Analysis Test of the true amplifier circuit independent of the source and load. The opposite figure shows this circuit with the source and load sections removed. Run an AC Network Analysis Test of this modified circuit with the exactly the same settings as in the previous case. The results are shown in the figure below. Note how the value of |s21| at 1GHz has jumped to 15.385dB this time around, while the total input and output reflection coefficients are still both below -10dB. This validates your design strategy based on the unilateral assumption. You will see in the next section that the computed values of |s21| (insertion loss or gain) is very close to the computed value of the power gain from the source to the load.