I am working on an audio amplifier for fun. The OP-AMP I chose is NE5534. I think I figured out most of the circuit, but the pin 5 and 8 confuses me.
Pin 5 is "External offset voltage adjustment" pin (output) Pin 8 is "External offset voltage adjustment" pin (input)
I haven't had the chance to understand this from the datasheet
It seems optional, so I am tempted to leave unconnected. However, perhaps I should break out the pin to a throughhole or a pad.
Since I am unsure what kind of capacitor/resistor is required, I don't know if I can use a generic 0804 type place holder for it.
Can someone please enlighten me?
[update] Ok, I found the description for the two pins:
The input offset voltage of operational amplifiers (op amps) arises from unavoidable mismatches in the differential input stage of the op-amp circuit caused by mismatched transistor pairs, collector currents, currentgain betas (β), collector or emitter resistors, and so on. The input offset pins allow the designer to adjust for these mismatches by external circuitry. These input mismatches can be adjusted by putting resistors or a potentiometer between the inputs as shown in Figure 10. A potentiometer can be used to fine tune the circuit during testing or for applications which require precision offset control. More information about designing using the input-offset pins, see Offset Voltage of Operational Amplifiers (SLOA045).
After reading the description, I must admit I am lost. Can you please explain what "mismatches in the differential input stage" is?