I have been studying circuit diagrams for simple op-amp based audio amplifiers. Many times I have seen an electrolytic capacitor used as a coupling capacitor in a circuit where neither end of it appears to have a higher potential than the other. All textbooks mention that electrolytics must be biased correctly i.e. that one end must carry the higher potential, to avoid damage to the capacitor.
So why then, in a circuit where it is unknown what potentials will exist at either end, is it acceptable to use a polarised component in this way? Surely the audio signal, which is charging and discharging this capacitor, spends as much time positive as it does negative, and if this is the case, no electrolytic capacitor would be 'happy' subjected to these constant reversals of potential across it?
So why then, in a circuit where it is unknown what potentials will exist at either end, is it acceptable to use a polarised component in this way? Surely the audio signal, which is charging and discharging this capacitor, spends as much time positive as it does negative, and if this is the case, no electrolytic capacitor would be 'happy' subjected to these constant reversals of potential across it?