The reference element forms the foundation of all voltage regulators since output voltage is directly controlled by the reference voltage. Variations in the reference voltage will be interpreted as output voltage errors by the error amplifier and cause the output voltage to change accordingly. To achieve the desired regulation, the reference must be stable for all variations in supply voltages and junction temperatures. There are several common techniques which can be used to solve design problems using integrated circuit regulators. Many of these techniques are discussed in the section of the text that outlines error contributions.
The sampling element monitors the output voltage and converts it into a level equal to the reference voltage. A variation in the output voltage causes the feedback voltage to change to a value which is either greater or less than the reference voltage. This voltage difference is the error voltage which directs the regulator to make the appropriate response and thus correct the output voltage change.
The error amplifier of an integrated circuit voltage regulator monitors the feedback voltage for comparison with the reference. It also provides gain for the detected error level. The output of the error amplifier drives the control circuit to return the output to the preset level.
All the previous elements discussed remain virtually unaltered regardless of the type regulator circuit. The control element, on the other hand, varies widely, depending upon the type of regulator being designed. It is the element that determines the classification of the voltage regulator; series, shunt, or switching. Figure 5-2 illustrates the three basic
control element configurations, each of which is discussed in detail. These elements contribute an insignificant amount of error to the regulator’s performance. This is because the sampling element monitors the output voltage beyond the control element and compensates for its error contributions. However, the control element directly affects parameters such as minimum input-to-output voltage differential, circuit efficiency, and power dissipation.