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How to design small hysteresis schmitter trig

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andy2000a

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schmitter circuit

I use CMOS circuit design & layout & simulation
have hysteresis schmitter equation ..

but my design range is small VH =3.55 VL= 3.45

and I use hspice sim find have large differnec on my circuit
 

schmitter op amp

theoritically, the hystersis loop is determined by the W/L of transistors and can be calculated but the small loop u need is very small and I think it will be process dependent!

maybe u need to change the architecture of your system or the idea behind it!

BEST!
 

schmitter trigger, single power op amp

but in single power OPA design
if my design range is Vh=2.55 Vl=2.45 ..

the OPA positive feedback resistor have large ration ..
I don't think OPA positiove feedback is good architecture ..
and schemitter is bad architecture ..

have any good architerure for hystersis circuit ?
 

schmitter trigger

Schmitt trigger levels will vary dependend on power , because of feedback supplied from OPA or any other IC output - which is directly depndent on Vcc .
The simplest is to make stable power or put zener diode with resistor on OPA otuput and then use this fixed output to connect schmitt feedback resistor .

In addition you can set trigger detection point independently - 2 diodes and 2 feedback resistors will be needed .

or you can use 2 comparators (one per threshold ) and decoding logic but input noise could be a problem - capsitors will be necessary but transient time will be decreased .
 

no zener diode can be use in CMOS design ..
and I find main problem is my circuit act as power_on reset detect ..
and schmitt trig can work well if Vcc is "fix"
but my circuit have Vcc ramp up ..

I also use 1 Comp but hysteresis volt 100mv is too small . I think
　maybe I need 2 comparator for work ..

or anyone can provide a power_on_reset circuit with hysteresis circuit for reference ..
 

If you just apply the schmitter trig in Power-On-Reset circuit,Why you need to design so small hysteresis range 100mv?
I think 40% of supply voltage is ok.
 

sorry ..
I am a designer .. not define spec. ..
I also think don't need so small
but define speci not by me ..

by the way .. have anyone design a comparator with hysteresis ?
maybe this comparator can met my speci ..
 

you can use one type comparator with hysteresis(use positive feedback).you can
adjust the W/L ratio to get the hysteresis you need.
you can find the comparator structure in any book that introduce comparator and opamp.hope this help you!
 

maybe your simulating list's sweep interstep is large
 

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