Circuit Idea/Functional Viewpoint

According to the heuristic approach, we should consider devices and elements at the functional level. The emphasis is not so much on their internal device but on their behavior in the studied scheme. The function that a given element performs determines its name. Presented this way, the transistor is a current source, a voltage-to-current or current-to-current converter, a comparator, a regulating element; the operational amplifier is a variable voltage source, and so on.

The function that an element performs also determines its name. For example, a variable resistor can perform the function of a potentiometer (aka voltage divideror voltage-to-voltage converter), displacement-to-voltage converter, analog multiplier. The inverting amplifier can be used as a voltage stabilizer, resistance-to-voltage converter, analog multiplier, divider, etc.. The R-2R ladder can act as a voltage-to-current converter, code-to-current converter or digitally controlled resistor.