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I am doing a process, voltage, temperature (PVT) analysis of an RC-based multi-vibrator. Simulations under varying temperature (0-100 C) and process corners (FF, FS, SF, SS) show signal delay in the modulated signals. This delay is due to the effect of temperature and process on R1, C1, and MOSFET's threshold voltage.

I used a PVT independent Schmitt trigger (ST) with fully adjustable threshold voltage to mitigate the modulated signal delay, but the ST does not work to mitigate delay.

Please comment: Is a PVT-independent ST a wise choice to mitigate signal delay? How can I create a PVT-independent modulated signal? Note: I implemented the circuit in CMOS 0.35 technology.

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  • \$\begingroup\$ Even IF that "PVT independent Schmitt trigger" is as PVT independent as they say (I am curious what the design is as I think there must be a catch) then your resistor and capacitor will not be PVT independent. You will suffer from PVT dependent delays etc. Real PVT dependent circuits usually have some form of calibration. \$\endgroup\$ Jun 7 at 16:09
  • \$\begingroup\$ And also, a diode in series with a gate input is a bad idea. No current can flow through the diode so what is the point of having that diode there? \$\endgroup\$ Jun 7 at 16:10
  • \$\begingroup\$ @Bimpelrekkie Regarding diode: actually it's an ST, not a diode. I draw the ST symbol wrong. The purpose of ST is to mitigate the possible variation due to PVT (according to my supposition/thinking ). \$\endgroup\$
    – Bam_Khel
    Jun 7 at 16:14
  • \$\begingroup\$ @Bimpelrekkie Two points (based on your first) I would like to discuss : 1_ (PVT independent Schmitt trigger): ST I used is robust but not ideal. the variation due to ST is minimum compared to the RC network. R and C I used are not PVT independent, due to which transient signal (depends on RC constant) shows delay. 2_I am wondering how to minimize transient signal delay so that I can get minimum variation in modulating signal. Your suggestion will help me to find an easy solution. Thanks. \$\endgroup\$
    – Bam_Khel
    Jun 7 at 16:25
  • \$\begingroup\$ What are your actual requirements for this circuit? What is the target frequency, and how much deviation is acceptable? What variations in supply voltage and temperature will your circuit experience? Off hand, I would be surprised if you can achieve better than 25% tolerance. \$\endgroup\$ Jun 8 at 1:02

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