Network, active device and interstage matching network. Termination is comprised of |Z.sub.S~ cascaded with the input matching Network 3, used for checking input stability of the second stage,Ĭonsists of the active device and output matching network. In addition to overallĪmplifier stability, the stability of each individual stage should be Impedances expected in the given application. ||Gamma~.sub.S~ and ||Gamma~.sub.L~ based on the source and load Overall amplifier stability is evaluated in the usual manner with Figure 2 shows the two-stage amplifier and the additionalĬircuitry necessary for checking input and output stability of the first
The usefulness of the alternative stability factor can be shown withĪn example. Where two parameters, that is k and |B.sub.1~, are required for aĭetermination of stability, the two parameters |K.sub.AS~ and |K.sub.AL~Īre necessary and sufficient in this design. Traditional stability factor, thus preserving the designer's These conditions correspond as much as possible to those of the |is less than~ 1 or |K.sub.AL~ |is less than~ 1 the network is unstable. Stable under the given source and load conditions, and for |K.sub.AS~ |is greater than~ 1 and |K.sub.AL~ |is greater than~ 1, the network is Aĭefinitive indication of stability is then provided as for |K.sub.AS~ Stability factor |K.sub.AL~ is determined in a similar manner. Value of~ |S|prime~.sub.22~ |is less than~ 1, the inside of the circle If |absolute value of~ |S|prime~.sub.22~ |is greater than~ 1, thenįollowing definition of a stability circle, the outside of the circle is ||Gamma~.sub.p~ = a test point chosen inside the stability circle Where either the outside or the inside of the stability circleĬorresponds to the stable region. The exponent |P,sub.s~ is introduced to account for the general case Therefore, the input alternative stability factor can be defined as It can be seen that this condition is met if the magnitude of theĭifference vector between Cs and ||Gamma~.sub.s~ is greater than Rs + From straightforward geometric considerations, ||Gamma~.sub.s~, with any associated uncertainty ||Delta~.sub.s~, must |Delta~ = |S.sub.11~|S.sub.22~-|S.sub.12~|S.sub.21~įor this circuit to be stable, the source reflection coefficient ||Delta~.sup.2~ - |absolute value of~ |S.sub.11~.sup.2~ (1)Īnd the radius of the stability circle by|1~ The vector to the center point of the stability circle is Purposes, it is assumed temporarily that the stable region is outside of ||Delta~.sub.s~ and other parameters of interest. Including the source reflection coefficient with uncertainty radius Stability and permits the design engineer to concentrate stabilityĬircle investigations on those frequency ranges where further insight isįigure 1 shows a Smith chart and source plane stability circle, |K.sub.A~ is presented that provides a definitive indication of Stable, but is in fact stable when operated within the range of expected Process can be tedious, particularly since k tends to predict falseĪlarms, that is, frequencies at which the network is not unconditionally Simultaneously with the source and load reflection coefficients. Stability circles must be computed.|2~ These circles are then displayed Unconditionally stable, and both a passive source and load are expected,
Must be determined to be stable.|4,5~ Unless the traditional stabilityįactor|6~ k in conjunction with|4~ |B.sub.1~ indicates that a network is Stability is an important consideration when designing anĪmplifier.|1-3~ Both the overall amplifier and each individual stage APA style: An alternative stability factor for amplifier design.An alternative stability factor for amplifier design." Retrieved from
#If stability circle outside smith chart free#
MLA style: "An alternative stability factor for amplifier design." The Free Library.
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