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The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category 'Functional'. The cookie is used to store the user consent for the cookies in the category 'Analytics'. These cookies ensure basic functionalities and security features of the website, anonymously. Necessary cookies are absolutely essential for the website to function properly. I hope all you SPICE jockeys enjoy Charles' little tutorial and you Apple nuts can check out his website for a nice simualtion tool. The above results used version v2.9p34 of MacSpice 3f5 which will be released and available from the MacSpice website soon after Easter in case you want to try it for yourself. However, if you wanted to build noise and bandwidth into the problem, I think MacSpice might give Excel a run for its money. The Excel spreadsheet could get a similar answer without much trouble. In this scenario, the cost function is much easier to calculate (it's just minus the range parameter) but procedure to evaluate the cost must also calculate the variation in gain over the range and reject (by signalling a constrint violation) the parameters if the variation exceeds 2dB.įor this example the MacSpice optimizer worked okay, but is probably overkill. In addition to the areas, the range is treated as an adjustable parameter. seven-to-one.Īnother way to tackle this problem with the MacSpice optimizer would be to treat it as a two-parameter optimization. The best value of the varied parameter p corresponds to a ratio of areas for the “N” and “1X” transistors of (1+ p )/(1− p ) = 7.08, i.e. The results are as follows: MacSpice 1 -> source Sauer:diffpair-optim.srcCircuit: diffpair ckt - offset differential pairOptimize begins:Plotname: optim1Method: Nelder-Mead SimplexCost function: Sauer:diffpair-cost.srcParameter(s): pStop when: ( Nevals > 100 ) or ( ÄCost This invokes the optimizer, and plots a sweep corresponding to the best value found. The plot created by the DC sweep is destroyed before returning, in order to conserve memory.ģ. It sets the cost to the value of the sweep variable at this point, and negates the optimizer minimizes cost, but we want the largest range. Starting at the zero-input gain, the procedure works along the sweep until the it finds the point where the variation in the gain is just within the specification set by the variable $ripple, 2dB in this case. It calculates the 'gain' of the amplifier from the derivative with respect to the sweep. If so, it alters the transistor areas, keeping the total area constant, and performs a DC sweep. This checks that the value of the parameter p, set by the optimizer, lies in an appropriate range. The cost function procedure 'diffpair-cost.src' The spreadsheet seemed to be a generic tool, so I've used a guessed model for the transistors, and named it 'generic'.Ģ.

Macspice tutorial