OpAmp selection table: rail-to-rail option misunderstanding

Question

Hello, 
 In the selection table for OpAmps for there are 3 values for "rail-to-rail" option: 
 
 Both 
 In to V- 
 Output 
 
 While the first two is quite comprehensive ( "true rail-to-rail" and "negative-only-rail" consequently), the 3rd I didn't understand. 
 What "Output" rail-to-rail mean exactly ? 
 Thanks

PaulCA · Accepted Answer

Hello Pavel47 , Rail-to-rail is a term used to describe an OpAmp that is capable of swinging near its supply voltages. This can refer to either the output or both the input and output of an OpAmp. 
 Output rail-to-rail means that the OpAmp's output can operate or swing near the positive and negative supply voltage rails. If we say that the OpAmp's output is rail-to-rail, it means that it is capable of driving its output very close to the supply rails regardless of whether its input is also rail-to-rail or not. Regards, Paul

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OpAmp selection table: rail-to-rail option misunderstanding

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