Whats the benefit of the rail to rail of opamp?

[minaflying]

rail to rail

Can some body tell me what's the benefit about the rail to rail of op.
thanks alot.
best Regard.

 

[Bluechem]

rail to rail

hi
maybe this helps
**broken link removed**

 

[flatulent]

Re: rail to rail

The application note in the post above will tell you all about the drawbacks of rail to rail amplifiers. The good point is that with low supply voltages you will still get a good input common mode range and output swing. With ordinary amplifiers they output can only go to withing about 1.5 V of either supply. With a 3 V supply there will be no output swing for instance.

 

[dwang_w]

Re: rail to rail

i think rail to rail is the output low is 0,and output high is supply

 

[Free_Will]

Re: rail to rail

Its benefit is to be able to work with full range of power supply.For example if somethnig is not rail-to-rail may mean for 5V system that you can limited with Minumum working voltage: 0.2V and 4.7V maximum voltage.(Say you can not meausure voltages below 0.2V if this will be an ADC)Note that these values are just examples...

 

[Rodres]

rail to rail

an op-amp sometimes has a rail to rail imput stage because it let large input common mode range and reasonable signal to noise ratio.

 

[leo_o2]

Re: rail to rail

It seems difficult to design a rail-to-rail opamp with consistent gain over all input range. Can anyone provide some suggestions for it?

 

[Rodres]

Re: rail to rail

It seems difficult to design a rail-to-rail opamp with consistent gain over all input range. Can anyone provide some suggestions for it?

Hello
I think that you can use a charge pump to improve your desing. Using this technique you can provides the local supply voltage for the input differential pair, so the input signal can swing between the rails (rail to rail).

I have a paper that explain this technique and use it in a design of a CMOS rail-to-rail input operational amplifier with THD performance of -90 dB which is suited for high-quality audio systems.

I could share it if you want.

 

[Rodres]

Re: rail to rail

This is de document. I hope it is useful.

 

[leo_o2]

Re: rail to rail

Please post here if this document is not big.

Thanks.

 

[ArchAngel]

rail to rail

rail refer to power and gnd, R-R can take the full use
of power supply range, this is very important for low
voltage application.