Loop-invariant expression

The best way to handle this case is to move the loop-invariant expression out of the loop. This also improves simulation efficiency. This is shown in the following example. 

The overall ability of a power supply to attenuate disturbances at its input is expressed as its PSRR (power supply rejection ratio). In graphs, PSRR is usually plotted as a function of frequency. We will invariably find that the rejection ratio is very low at higher frequencies. One reason for this is that the Bode plot cannot really help because the open-loop gain is very small at these frequencies. The other reason is, even a tiny stray parasitic capacitance (e.g., across the power switch and inductor) presents such a low impedance to noise frequencies (whatever their origin) that almost all the noise present at the input migrates to the output unimpeded. In other words, the power stage attenuation (which we had earlier declared to be Vo/Rin) is also nonexistent for noise (and maybe even ripple) frequencies. The only noise attenuation comes from the LC filter (hopefully). 

The next correction of order a Za.)EF is generated by the gauge invariant set of diagrams in Fig. 9.8(c). The respective analytic expression is obtained from the skeleton integral by simultaneous insertion in the integrand of the one-loop polarization function Ii k) and of the electron factor F k). 

The right-hand-side expression in the assignment statement is invariant of the loop index, that is, the value computed in variable Up is independent of the loop index Count. However, a synthesis tool may generate five sub-... 

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