Separating and Managing AC and DC Gain
3.1 A Small Complication
The previous chapter showed basic op amp gain circuits. There is another aspect to op amp design, one which complicates things. Op amps will amplify DC voltage just as readily as AC voltage. Low-level instrumentation circuits generate their own slight DC offset voltage, which is also amplified by the gain of the circuit. Op amp circuits designed to amplify only AC signals can be constructed with coupling capacitors to block any unwanted DC voltage from being amplified in subsequent stages, which is commonly done in high-gain signal paths. However, this is not acceptable in circuits that must provide the proper DC as well as AC levels.
3.2 Single Supply versus Dual Supply ...
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