Issue link: https://resources.pcb.cadence.com/i/1180526
PSpice User Guide Analog behavioral modeling October 2019 352 Product Version 17.4-2019 © 1999-2019 All Rights Reserved. When the template substitution is performed, the resulting VALUE is equivalent to the following: V = V(grid, cathode) + 0.12*V(anode, cathode) The part would be defined with the following characteristics: EXP1 = V(%IN2,%IN3)+ EXP2 = 0.12*V(%IN1,%IN3) This works for the main operating region but does not model the case in which the current stays 0 when combined grid and anode voltages go negative. We can accommodate that situation as follows by adding the LIMIT part with the following characteristics: HI = 1E3 LO = 0 This part instance, LIMIT1, converts all negative values of v g +.12*v a to 0 and leaves all positive values (up to 1 kV) alone. For a more realistic model, we could have used TABLE to correctly model how the tube turns off at 0 or at small negative grid voltages. We also need to make sure that the current becomes zero when the anode alone goes negative. To do this, we can use a DIFF device, (immediately below the ABM3 device) to monitor the difference between V(anode) and V(cathode), and output the difference to the TABLE part. The table translates all values at or below zero to zero, and all values greater than or equal to 30 to one. All values between 0 and 30 are linearly interpolated. The properties for the TABLE part are as follows: ROW1 = 00 ROW2 = 301 The TABLE part is a simple one, and ensures that only a zero value is output to the multiplier for negative anode voltages. The output from the TABLE part and the LIMIT part are combined at the MULT multiplier part. The output of the MULT part is the product of the two input voltages. This value is then raised to the 3/2 or 1.5 power using the PWR part. The exponential property of the PWR part is defined as follows: EXP = 1.5 The last major component is an ABM expression component to take an input voltage and convert it into a current. The relevant ABM1/I part property looks like this: