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# What is rail-to-rail supply voltage?

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#### Syukri

##### Full Member level 5
Is it the voltage swing of the device?

One picture can be worth more that one million words ..

Regards,
IanP

mehdi_rfid

### mehdi_rfid

Points: 2
ye very good pic

i think an ac supply to an opamp is a bad example to set

and an open ended opamp has infinite gain so its not i/o levels shown

rail to rail is simple

this is called a floating ground setup

and rail to rail is

the voltage between ( (+rail and gnd) + (-rail to gnd)) = volts = rail to rail level

a good example in ac systems is a split secondary tap

where you have one coil {transformer}

split in the middle this 'tap' is then used as a common rail
each end is a rail so rail to rail is the voltage between each end and the tap added together to give rms voltage split rail

Syukri,
Rail to rail supply voltage is the voltage between the + and - supply voltages of a device. When authors refer to "rail-to-rail output" capability, they mean that the devices is capable of providing outputs that are equal to the positive and negative supply (rail) voltages. When they refer to "rail-to-rail input" capability, they mean that the device is capable of operating with inputs that are equal to the positive and negative supply voltages.
Regards,
Kral

Points: 2

### Harish Achar

Points: 2
Rail to rail voltage is |V+| + |V-| value.

Hello ,

rail-to-rail supply voltage is the voltge from most +V of the circuit to the most -V of the circuit. As example , from Vdd to ground (when it's the max. supply voltage to the circuit).
Thanx

The input range is vdd to ged or -vdd

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