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OP Amps are the building blocks from which most of today's audio gear is built. This is less so in High-End audio, wherein discrete holds sway over the IC; excepting CD players and surround sound processors, here the OP Amp and the IC rule.
What is a operational amplifier? The perfect operational amplifier is easy to define: infinite bandwidth, infinite input impedance, zero output impedance, infinite gain, infinite slew rate, and an input and output voltage swing equal to its power supply rail voltages. Well, in point of fact, today's OP Amps come close to this ideal. And it is this near perfect functioning that allows us to treat them as simply a generic function-- namely, an operational amplifier. We don't have to worry about what goes on inside the Op Amp, only about what its function is in the circuit: inverting or non-inverting and so on. Audio Gadgets helps in design of this circuit by showing the effect of component changes or, in the case of specifying a desired gain, the component values needed.
Buffer
The Buffer OP-Amp configuration is useful for inter-stage isolation or impedance matching between stages. A simpler circuit can not be imagined; just tie the output to the inverting input of the amp and that's it. Furthermore, some IC's are design to be buffers and only buffers, i.e., LM310, LH0033, which may prove a closer approximation to the perfect Buffer and come pre-configured. Consequently, there is not much here for Audio Gadgets to crunch on.
Current to Voltage
The I to V configuration converts an input current into an output voltage. Almost all CD player contain such a stage as the output from most D to A converters is a current output, not voltage. If an oscilloscope's probe is attached to the input of the I to V converter, nothing much can be seen in the trace, as there should be zero voltage at that point. The voltage occurs at the output, as any current traveling through a resistance will define a voltage--Ohm's law, once again.
Differential Amplifier
The Differential OP-Amp configuration has two inputs, one inverting and one non-inverting. A signal that is common to both inputs is largely ignored, while a difference in signals is amplified. Inside a surround sound decoding box is where you might find a Differential Amplifier being used, as both the right channel and the left channel signals can be fed into the two inputs of this circuit, whose output will then be one channel minus the other. In other words, what was common to both channels will drop out of the resulting signal and one channel's signal will remain in phase, but the other will experience a phase reversal.
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