This is the voltage controlled switch in the LTspice.

VCS Schematic

Is there a switch which can replace it? I need a switch for a schematic. At first, I used a transmission gate switch, but the simulation of the circuit was different than it was when using a voltage controlled switch. I want to convert a circuit from LTspice to Cadence Virtuoso, but I don't know if there is a suitable part.

I use the hspice in the Cadence Virtuoso

The size of NMOS and PMOS in the transmission gate switch is 18µ/180n and 36µ/180n. If this size is not good, please let me know. Thank you.

  • \$\begingroup\$ Using MOS switches is fine, but you need to tweak your values, maybe edit your schematic. For example, The signal at the input is both positive and negative in value, do you think a single ended supply will do? \$\endgroup\$ Commented Apr 28, 2018 at 7:11
  • \$\begingroup\$ i don't understand about "The signal at the input is both positive and negative in value",can you take an example? \$\endgroup\$
    – XM551
    Commented Apr 28, 2018 at 7:28
  • \$\begingroup\$ I have updated the answer to that previous question. \$\endgroup\$ Commented Apr 28, 2018 at 7:29
  • \$\begingroup\$ The size of MOS i think is suitable for the switch,i can't modify it to the better one \$\endgroup\$
    – XM551
    Commented Apr 28, 2018 at 7:29
  • 1
    \$\begingroup\$ This question is bad asked, in my opinion. What you want to do is design a pass/transmission gate on silicon with a certain PDK. The fact that the ideal component is available in ltspice is not relevant. What is relevant is the specification of the pass gate you want to design, I would start from Ron and maybe bandwidth, then there is area constraint, what voltages you have available to turn on the gates, charge injection... It certainly is not possible to design the ltspice SW component on silicon, because SW is ideal, silicon tend to be real instead. \$\endgroup\$ Commented Apr 28, 2018 at 9:37

1 Answer 1


Evaluate the characteristics of the existing voltage controlled switch, then select a switch with the same characteristics, otherwise the simulation output will change based on the different characteristics.

  • \$\begingroup\$ i don't know its characteristic,because i can't use the ltspice,so i ask here and want to know does anyone know? \$\endgroup\$
    – XM551
    Commented Apr 28, 2018 at 6:30
  • \$\begingroup\$ You say that v-c switch is in LT Spice - so if it exists in the program it will have the specs.... \$\endgroup\$
    – Solar Mike
    Commented Apr 28, 2018 at 6:33
  • \$\begingroup\$ that vc switch doesn't exist in cadence virtuoso \$\endgroup\$
    – XM551
    Commented Apr 28, 2018 at 6:35
  • 1
    \$\begingroup\$ If you're asking how to model something in Virtuoso, you should mention that in your actual question. \$\endgroup\$
    – The Photon
    Commented Apr 28, 2018 at 6:36
  • \$\begingroup\$ So you should edit your question and explain that you are converting a circuit from LTSpice to Cadence Virtuoso - this is crucial information that you have not included.... \$\endgroup\$
    – Solar Mike
    Commented Apr 28, 2018 at 6:37

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