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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?

#### IanP

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

Regards,
IanP

mehdi_rfid

### mehdi_rfid

Points: 2

#### VSMVDD

##### Banned
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

#### Kral

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

#### Davood Amerion

Rail to rail voltage is |V+| + |V-| value.

#### mohazaga

##### Full Member level 2
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

#### pillar_chen

##### Member level 3
The input range is vdd to ged or -vdd

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