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How to desig Hi volt bandgap circuit ??

 
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andy2000a



Joined: 18 Jul 2001
Posts: 756
Helped: 7
Post19 Aug 2004 2:45   How to desig Hi volt bandgap circuit ??
which type bandgap is suit for large swing @power supply
Vcc from 5~20v
someone said "SONG " architecture is cascode bandgap but
in gernel CKT unse 2 pmos + 1 nmos + bjt cascode
when Vcc from 5~ 20v .. V(bandgap) in not good ..
and use OPA + 2 diode architecture is better

I design a "SONG cascode bandgap " -> CMOS circuit design layout & simulation fig-21.14 , but when I sweep Vcc .. bandgap voltage
have large drift .. if I hope output can keep 1.25v .. mos bias=20u
how should I do ??
enlarge Pmos Length ? more series Pmos ??

I find many cmos analog design book talk about bandgap .. but no more detail description on it ..
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selvaraja



Joined: 01 Jun 2004
Posts: 218
Helped: 3
Post16 Oct 2004 6:47   Re: How to desig Hi volt bandgap circuit ??
hi

try put pmos in series ....hope this migth help you

regards,

selvaraja
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Hughes



Joined: 10 Jun 2003
Posts: 712
Helped: 84
Post16 Oct 2004 9:33   How to desig Hi volt bandgap circuit ??
Maybe we can design a simple voltage regulator to drive the supply of the bandgap.
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Fom



Joined: 10 Mar 2004
Posts: 758
Helped: 56
Location: Taiwan
Post16 Oct 2004 9:40   Re: How to desig Hi volt bandgap circuit ??
But if this voltage regulator will use bandgap for regulation there will be start up problem. Bandgap doesn't work because voltage regulator voltage is to low. But voltage regulator voltage is low because bangap doesn't work (not start up).
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Hughes



Joined: 10 Jun 2003
Posts: 712
Helped: 84
Post16 Oct 2004 14:31   How to desig Hi volt bandgap circuit ??
But you may use another coarse voltage reference (may be another bandgap using outer vdd as supply) to bias the voltage regulator. In fact, a voltage reference as simple as a diode-connected mosfet can meet the requirements for the voltage regulator.
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sunking



Joined: 25 May 2004
Posts: 914
Helped: 46
Post18 Oct 2004 5:41   Re: How to desig Hi volt bandgap circuit ??
What you mean is improve the PSSR of the bandgap.
Try add an OPA for the bandgap, you will improve the Chara. largely.
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arsenal



Joined: 17 Oct 2004
Posts: 134
Helped: 11
Post18 Oct 2004 5:52   How to desig Hi volt bandgap circuit ??
you can use a cascode to generate a sub-vdd as the supply for the bandgap, and the compensation for the ota should be ahuja
try it
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leo_o2



Joined: 03 Sep 2004
Posts: 330
Helped: 20
Post18 Oct 2004 9:43   Re: How to desig Hi volt bandgap circuit ??
What kind of process do you use? If there is some device with high voltage Vds (20V) and low voltage Vgs(5V), it should be fine. I also agree start-up circuit is your challendge for you.
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yargo



Joined: 15 Jan 2003
Posts: 5
Post19 Oct 2004 18:55   Re: How to desig Hi volt bandgap circuit ??
To solve startup problem you could use a startup circuit: in this way you may use the bandgap itself as a reference for the pre-regulator.
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lijun_sun



Joined: 11 Aug 2004
Posts: 7
Location: xiamen
Post20 Oct 2004 5:46   Re: How to desig Hi volt bandgap circuit ??
i just finished a cascode bandgap.output 1.22v TC=18ppm

startup voltage 2.7v

Vomax=17v
Maybe you can design a better one!

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cetc1525



Joined: 08 Oct 2004
Posts: 177
Helped: 3
Post22 Oct 2004 14:04   Re: How to desig Hi volt bandgap circuit ??
can you send the schematic or the structure&which tech did you use?
if your line regulation is big,you should reduce lamda,and use transistor with high early voltage .
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