Editing Operational amplifier (section)

=== Non-linear characteristics ===

==== Input breakdown voltage ====
The transistors Q3, Q4 help to increase the reverse ''V''<sub>BE</sub> rating; The base-emitter junctions of the NPN transistors Q1 and Q2 break down at around 7{{nbsp}}V, but the PNP transistors Q3 and Q4 have ''V''<sub>BE</sub> breakdown voltages around 50{{nbsp}}V.<ref>[http://ecow.engr.wisc.edu/cgi-bin/get/ece/342/schowalter/notes/chapter10/theua741operationalamplifier.ppt The μA741 Operational Amplifier]{{dead link|date=June 2016|bot=medic|fix-attempted=yes}}{{cbignore|bot=medic}}</ref>

==== Output-stage voltage swing and current limiting ====
Variations in the quiescent current with temperature, or due to manufacturing variations, are common, so [[crossover distortion]] may be subject to significant variation.

The output range of the amplifier is about one volt less than the supply voltage, owing in part to ''V''<sub>BE</sub> of the output transistors Q14 and Q20.

The {{val|25|u=Ω}} resistor at the Q14 emitter, along with Q17, limits Q14 current to about {{val|25|u=mA}}; otherwise, Q17 conducts no current. Current limiting for Q20 is performed in the voltage gain stage: Q22 senses the voltage across Q19's emitter resistor ({{val|50|u=Ω}}); as it turns on, it diminishes the drive current to Q15 base. Later versions of this amplifier schematic may show a somewhat different method of output current limiting.