The ALTEL record provides altered circuit element values for a subsequent analysis. The format for the ALTEL record is:
.ALTEL name1 value1 name2 value2 ...
where namei is a text element name and must refer to an existing circuit element and valuei is a real value which is to replace the current value for element namei. The values for resistors, capacitors, inductors, VCC elements, CCC elements, VVC elements, CVC elements, I sources, and V sources can be .ALTered. The phase for I and V sources cannot be .ALTered.
The .ALTEL record must appear after the CKT - END section.
The use of multiple line records is allowed with .ALTEL records. The effect of .ALTEL records is accumulative since the circuit element values are not restored to the original values after an .ALTered circuit is analyzed. Multiple .ALTEL records can be used to alter large numbers of circuit elements.
The changes specified on .ALTEL records are not effective until a subsequent .ALTGO or .GO record is processed.
Example:
.ALTEL r45 2.385e3 ein 2.5 \
c3 1.55e-8
After the above record the current circuit (defined by a previous .CKT - .END section) will contain modified element values for the elements r45, ein, and c3. The elements r45, c3, and ein must have been defined in the previous .CKT - .END section. The .ALTered circuit will be analyzed when an .ALTGO or .GO record is encountered. The values of any altered elements are scaled according to the current .FSCALE and .ZSCALE parameters, if any.
Only if a legal .ALTEL record is encountered will the alteration number of the run be incremented.
Note that calculated values must be handled carefully. Because of the implementation, the following record will not do what is implied:
.ALTEL r3 100. r4 { r3 199. X }
The value of r3 used to calculate r4 will be the value that existed before this .ALTEL record. To use the altered value for r3, simply use two .ALTEL records:
.ALTEL r3 100.
; previous records updates value for r3
; new value of r3 is used in:
.ALTEL r4 { r3 199. X }