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gnucap:manual:devices:basic:posy [2015/12/11 15:39] (current) |
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+ | ====== "posy" Polynomial with non-integer powers ====== | ||
+ | |||
+ | ===== Syntax ===== | ||
+ | |||
+ | posy c1,p1 c2,p2 ... | ||
+ | posy c1,p1 c2,p2 ... args | ||
+ | |||
+ | ===== Purpose ===== | ||
+ | |||
+ | Defines a transfer function by a one dimensional ``posynomial'', like | ||
+ | a polynomial, except that the powers are arbitrary, and usually non-integer. | ||
+ | |||
+ | ===== Comments ===== | ||
+ | |||
+ | There is no corresponding capability in any SPICE that I know of. | ||
+ | |||
+ | For capacitors, this function defines //charge// as a function of | ||
+ | voltage. For inductors, it defines //flux// as a function of | ||
+ | current. | ||
+ | |||
+ | For fixed sources, it defines voltage or current as a function of | ||
+ | time. | ||
+ | |||
+ | Normal use of this function required positive input (voltage or | ||
+ | current). The result is zero if the input is negative. Raising a | ||
+ | negative number to a non-integer power would produce a complex result, | ||
+ | which implies a non-causal result, which cannot be represented in a | ||
+ | traditional transient analysis. | ||
+ | |||
+ | The transfer function is defined by: | ||
+ | |||
+ | <code> | ||
+ | if (in >= 0){ | ||
+ | out = (c1*in^p1) + (c2*in^p2) + .... | ||
+ | }else{ | ||
+ | out = 0. | ||
+ | } | ||
+ | </code> | ||
+ | |||
+ | ===== Parameters ===== | ||
+ | |||
+ | |min |Minimum output value (clipping). (Default = -infinity) | | ||
+ | |max |Maximum output value (clipping). (Default = infinity) | | ||
+ | |abs |Absolute value, truth value. (Default = false). If set to true, the result will be always positive. | | ||
+ | |odd |Make odd function, truth value. (Default = false). If set to true, negative values of x will be evaluated as out = -f(-x), giving odd symmetry. | | ||
+ | |even |Make even function, truth value. (Default = false). If set to true, negative values of x will be evaluated as out = f(-x), giving even symmetry. | | ||
+ | |||
+ | ===== Example ===== | ||
+ | |||
+ | E1 (2 0 1 0) posy(1 .5) | ||
+ | The output of E1 is the square root of its input. | ||