Hi all!

The ramp function from my ramp generator is an input to a comparator(vin-) and another input is vref = 0.45V(vin+), the resulting wave is a square wave with 50% duty cycle.

Now when I made a schematic of bandgap voltage reference(attached image) and simulate it I have difficulty having an output of Vref = 0.45V, I can only get 0.8V-1V vref no matter how much I change the resistors.

My source voltage is 1.2Vdd.

I try using the formula(attached image), but I don't really know what is Vt and n. I assume it is my source voltage and bjt ratio of areas. Please enlighten me.

Also if you can recommend some better bandgap voltage reference I would really appreciate it.

Thank you very much for taking time reading this:thumbsup:

 

Some ref material -

https://www.google.com/url?sa=t&rct...ep1&type=pdf&usg=AOvVaw2XyOgFh7cZg9jn-DxJFvIQ

https://wiki.analog.com/university/courses/electronics/text/chapter-14


Regards, Dana.

 

Some ref material -

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&ved=0ahUKEwjbstXk8qzaAhUQ8YMKHdiWDi4QFgheMAY&url=http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.855.6814&rep=rep1&type=pdf&usg=AOvVaw2XyOgFh7cZg9jn-DxJFvIQ

https://wiki.analog.com/university/courses/electronics/text/chapter-14

Thanks, bandgap voltage reference only outputs vref = 1.2V right? Is there any way I can lower that to 0.45V? If not what are my options other than bandgap?



Regards, Dana.

 

Yes thru a precision divider/buffer arrangement.

Regards, Dana.

 

Yes thru a precision divider/buffer arrangement.

Regards, Dana.

Do you have existing paper about precision divider? Or can you recommend something to read about that?

 

Are you doing an actual silicon design or a discrete approach ?

Insofar as papers,. the IEEE library has a ton of papers on silicon
design, I am sure you could find ref material there. Unfortunatly its
a paid for library, membership required. You might search archive.org
and the nasa library to see if you can find anything.

Precision divider, I was thinking for discrete design you would need
high precision resistors - http://www.caddock.com/Online_catalog/networks/networks.html
The buffer would be a low drift/offset OpAmp. Onchip design would be laser trimmed
poly resistors.

Regards, Dana.