Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Whats the benefit of the rail to rail of opamp?

Status
Not open for further replies.

minaflying

Junior Member level 2
Joined
Sep 24, 2004
Messages
22
Helped
2
Reputation
4
Reaction score
0
Trophy points
1,281
Activity points
174
rail to rail

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

flatulent

Advanced Member level 5
Joined
Jul 19, 2002
Messages
4,629
Helped
489
Reputation
980
Reaction score
150
Trophy points
1,343
Location
Middle Earth
Activity points
46,689
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

Member level 1
Joined
Aug 14, 2004
Messages
34
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,286
Activity points
299
Re: rail to rail

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

Free_Will

Member level 3
Joined
Apr 6, 2002
Messages
65
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,288
Activity points
581
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

Junior Member level 2
Joined
Sep 26, 2004
Messages
21
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,281
Activity points
220
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

Advanced Member level 4
Joined
Sep 3, 2004
Messages
1,324
Helped
277
Reputation
556
Reaction score
241
Trophy points
1,343
Location
China
Activity points
5,761
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

Junior Member level 2
Joined
Sep 26, 2004
Messages
21
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,281
Activity points
220
Re: rail to rail

leo_o2 said:
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

Junior Member level 2
Joined
Sep 26, 2004
Messages
21
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,281
Activity points
220
Re: rail to rail

This is de document. I hope it is useful.
 

leo_o2

Advanced Member level 4
Joined
Sep 3, 2004
Messages
1,324
Helped
277
Reputation
556
Reaction score
241
Trophy points
1,343
Location
China
Activity points
5,761
Re: rail to rail

Please post here if this document is not big.

Thanks.
 

ArchAngel

Member level 1
Joined
Jul 1, 2004
Messages
39
Helped
2
Reputation
4
Reaction score
1
Trophy points
1,288
Activity points
187
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.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top