Editing Operational amplifier (section)

=== Other linear characteristics ===

==== Overall open-loop gain ====
The net open-loop small-signal voltage gain of the op amp is determined by the product of the current gain ''h''<sub>fe</sub> of some 4 transistors. In practice, the voltage gain for a typical 741-style op amp is of order 200,000,<ref name="NS LM741" /> and the current gain, the ratio of input impedance (~2−6{{nbsp}}MΩ) to output impedance (~50{{nbsp}}Ω) provides yet more (power) gain.

==== Small-signal common mode gain ====
The ideal op amp has infinite [[common-mode rejection ratio]], or zero common-mode gain.

In the present circuit, if the input voltages change in the same direction, the negative feedback makes Q3/Q4 base voltage follow (with 2 ''V''<sub>BE</sub> below) the input voltage variations. Now the output part (Q10) of Q10-Q11 current mirror keeps up the common current through Q9/Q8 constant in spite of varying voltage. Q3/Q4 collector currents, and accordingly the output current at the base of Q15, remain unchanged.

In the typical 741 op amp, the common-mode rejection ratio is 90&nbsp;dB,<ref name="NS LM741" /> implying an open-loop common-mode voltage gain of about 6.<!-- 200,000 / 10^^(4.5) -->

==== Frequency compensation ====
The innovation of the Fairchild μA741 was the introduction of [[frequency compensation]] via an on-chip (monolithic) capacitor, simplifying application of the op amp by eliminating the need for external components for this function. The 30&nbsp;pF capacitor stabilizes the amplifier via [[Miller effect|Miller compensation]] and functions in a manner similar to an op-amp [[integrator]] circuit. Also known as ''dominant [[Pole (complex analysis)|pole]] compensation'' because it introduces a pole that masks (dominates) the effects of other poles into the open loop frequency response; in a 741 op amp this pole can be as low as 10&nbsp;Hz (where it causes a −3&nbsp;dB loss of open loop voltage gain).

This internal compensation is provided to achieve [[BIBO stability|unconditional stability]] of the amplifier in negative feedback configurations where the feedback network is non-reactive and the [[loop gain]] is [[unity (mathematics)|unity]] or higher. In contrast, amplifiers requiring external compensation, such as the μA748, may require external compensation or closed-loop gains significantly higher than unity.

==== Input offset voltage ====
The ''offset null'' pins may be used to place external resistors (typically in the form of the two ends of a potentiometer, with the slider connected to ''V''<sub>''S''–</sub>) in parallel with the emitter resistors of Q5 and Q6, to adjust the balance of the Q5/Q6 current mirror. The potentiometer is adjusted such that the output is null (midrange) when the inputs are shorted together.