[1][2] The open-loop gain of many electronic amplifiers is exceedingly high (by design) – an ideal operational amplifier (op-amp) has infinite open-loop gain.
Typically an op-amp may have a maximal open-loop gain of around
An op-amp with a large open-loop gain offers high precision when used as an inverting amplifier.
Normally, negative feedback is applied around an amplifier with high open-loop gain, to reduce the gain of the complete circuit to a desired value.
The definition of open-loop gain (at a fixed frequency) is where
Take the case of an inverting operational amplifier configuration.
and the resistor between a source voltage and the inverting input node is
The open-loop gain of an operational amplifier falls very rapidly with increasing frequency.
Along with slew rate, this is one of the reasons why operational amplifiers have limited bandwidth.