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' If you do not allow these cookies, you will experience reduced relevant content.The spreadsheet seemed to be a generic tool, so I've used a guessed model for the transistors, and named it 'generic'.Ģ. They do not store directly personal information, but are based on uniquely identifying your browser and internet device. They may be used by Analog Devices to build a profile of your interests and show you relevant content on our site. Targeting Cookies: These cookies may be set through our site by Analog Devices and our service providers. If you do not allow these cookies we will not know when you have visited our site, and will not be able to monitor its performance. All information these cookies collect is aggregated and therefore anonymous.
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