#Stability circles on smith chart series
circles further onto the smith chart, is to add a series resistor at the. What is it about MSG that makes it the final word on stable gain when, I'll say, the 23 or even the 26dB gain circle seems safely out of the output stability circle's unstable region and seems like there would still be some safe terminating impedances, although not many, available.Graphical calculator or nomogram designed for electrical and electronics engineers specializing in radio frequency (RF) engineering to assist in solving problems with transmission lines and matching circuits Figure 6 (a) De-embedded HMC454ST89 amplifier S-parameters (b) Stability factor. Apparently, gain seems to be infinite with respect to a potentially unstable transistor. For conditional finding the stable region can be facilitated by using Smith chart and p1otting the input or output. Only when I jumped to 50 and 100dB did the gain circles just align with the output stability circle. coordinates that i got for input & output port of transistor are 1)for input centre 1. sc SmithChart() plotSStabCircle(sc,LNA,800e6,labelSource Stability). The 29dB gain circle is dangerously close to but still outside the output stability circle's unstable region. (Figures 7, 8, and 9) see Smith et al., 1996 Pontrelli et al., 1999 Giannoni et al. The results from the ADS simulation (Figure 3) shows that the device is conditionally stable as the stability circles clip the edge of the smith chart so. Now we can plot the the source and load stability circles on a smith chart. For the heck of it, I plotted gain circles all the way up to the ludicrous values of 50 and 100dB to see what would happen. Stability circles are a tool, used to examine and analyze the stability of an amplifier (in the case under discussion) using a graphical technique, with the. If anyone has any easy tutorial or suggestions for a test on monday. Notice that some of the 22.1dB constant-gain circle is located pretty far away and outside of the output stability circle's unstable region. Hi, I need help on plotting stability circles on a smith chart. In that sense input and output stability circles were plotted on the smith chart and the conclusion was that the transistor is potentially unstable as shown in Fig. I have the output stability circle plotted and the unstable region marked as UR on the Smith chart. and plot the stability circles on a Smith chart. The on-line article also said that "one should never try to tease more gain from the transistor than the MSG". We can derive the equation for the output stability circle as follows. For my transistor, the MSG in absolute gain 162.5 or 22.1dB as shown on the attached Smith chart. To complete our Smith chart, we superimpose the two circles families. Fundamentals of impedance and the Smith chart. ensuring quality factor impact, and assessing stability analysis. MSG is simply the ratio of the magnitude of S21 over the magnitude of S12. Keywords: smith chart, RF, impedance matching, transmission line. I recently read on-line that for a potentially unstable transistor the maximum gain that can achieved is the MSG or maximum stable gain. I was plotting constant-gain circles on the Smith chart the other day for a potentially unstable RF transistor.
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