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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 , or 100 dB. An op-amp with a large open-loop gain offers high precision when used as an inverting amplifier. Normally, negative ...
The DC and low-frequency gain of a transimpedance amplifier is determined by the equation =, so = If the gain is large, any input offset voltage at the non-inverting input of the op-amp will result in an output DC offset. An input bias current on the inverting terminal of the op-amp will similarly result in an output offset.
The net open-loop small-signal voltage gain of the op amp is determined by the product of the current gain h fe of some 4 transistors. In practice, the voltage gain for a typical 741-style op amp is of order 200,000, [16] and the current gain, the ratio of input impedance (~2−6 MΩ) to output impedance (~50 Ω) provides yet more (power) gain.
More generally, PM is defined as that of the amplifier and its feedback network combined (the "loop", normally opened at the amplifier input), measured at a frequency where the loop gain is unity, and prior to the closing of the loop, through tying the output of the open loop to the input source, in such a way as to subtract from it.
A more precise statement of this is the following: An operational amplifier will oscillate at the frequency at which its open loop gain equals its closed loop gain if, at that frequency, The open loop gain of the amplifier is ≥ 1 and; The difference between the phase of the open loop signal and phase response of the network creating the ...
An operational amplifier is an amplifier circuit which typically has very high open loop gain and differential inputs. Op amps have become very widely used as standardized "gain blocks" in circuits due to their versatility; their gain, bandwidth and other characteristics can be controlled by feedback through an external circuit. Though the term ...