how to realize a rail-to-rail amplifier in low supply-voltag

[leebluer]

icmr rail to rail

I need to design a rail-to-rail ICMR amplifier in low supply voltage. I find in almost the papers the rail-to-rail amplifier(eg, n-different input) is stressed on high ICMR, but i need much lower ICMR for n-different input amplifier. i am confused about the demand. Please give me some advice.
thanks

 

[yeechyan]

Use complementary configuration. (NPN & PNP or NMOS & PMOS) Complementary configuration enables you to acheive rail-to-rail input range. i.e. n-transistors conduct for the positive half cycle while p-transistors conduct for the negative half cycle.

 

[leebluer]

Re: how to realize a rail-to-rail amplifier in low supply-vo

Could you recommend some papers or others for me? I want to get detailed info.

Thanks & B. R.

 

[uladz55]

Re: how to realize a rail-to-rail amplifier in low supply-vo

Here some circuits examples

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[terryssw]

Re: how to realize a rail-to-rail amplifier in low supply-vo

NMOS + PMOS Diff. pair have some problems that the transcondutance of the opamp is not constant over the wide-range of input common mode range. This will produce large distortion (e.g. used in unity-gain buffer configuration). Certain type of contant gm controling circuit must be added (increase complexity, and they seems don't work under low supply voltage)

Also, as the supply voltage continues goes down (~ 1.5V), even NMOS + PMOS Diff. pair cannot cover the entire ICMR since there is a dead band at the mid-range of supply where both diff. pair cannot be turned on. Actually, now there is less good solutions to design rail-to-rail input CMOS op-amp under low-voltage conditions (<1.5V).

 

[isaacnewton]

Re: how to realize a rail-to-rail amplifier in low supply-vo

There is a good book:
Operational Amplifiers - Theory and Design
by Johan H. Huijsing
Kluwer Academic Publishers

 

[simonkuo]

Re: how to realize a rail-to-rail amplifier in low supply-vo

You can try to design the adapter between the input and complementary input stage or if your voltage is smaller than 1V, it will have the dead zone (the input stage does not work).

 

[cetc1525]

find papers on ieee.I think u should use cascode structure

 

[chinito]

Re: how to realize a rail-to-rail amplifier in low supply-vo

You can try an AB type output stage. That'll get you pretty close to the rails.

 

[yyliang]

Re: how to realize a rail-to-rail amplifier in low supply-vo

you can get a refernce from 《CMOS ANALOG INTERGRATED CIRCUITS DESIGN》by behzad razavi.use complimentary configuration is proposed in hte book.

 

[songsong]

J. Francisco Duque-Carillo, et al., "1-V Rail-to-rail operational amplifiers in standard cmos technology," JSSC, vol. 35, no. 1, Jan 2000.