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Voltage Gain

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The open-loop voltage gain of an operational amplifier is defined as the ratio of output voltage to input voltage measured with no external feedback applied. Open-loop voltage gain may thus be thought of as the 'internal' voltage gain of the device. In practice, this value is exceptionally high (typically greater than 100,000) but is liable to considerable variation from one device to another.

Open-loop voltage gain is the ratio of output voltage to input voltage measured without feedback applied, hence:

A_VOL = V_OUT/V_IN

where A_VOL is the open-loop voltage gain, V_OUT and V_IN are the output and input voltages respectively under open-loop conditions. In linear voltage amplifying applications, a large amount of negative feedback will normally be applied and the open-loop voltage gain can be thought of as the internal voltage gain provided by the device.

The open-loop voltage gain is often expressed in dB rather than as a ratio. In this case:

A_VOL = 20log₁₀(V_OUT/V_IN)

<^< Dual Supply Configurations | Course index | Worksheet: Voltage Gain >^>