Such circuits, voltage regulators, in practice, are used quite often.
They allow you to collect the source of stabilized voltage of 5 volts without spending time and with a minimum of additional components. This provides the maximum output current to 3 amps, but this is not always enough.
In this case, the scheme often add powerful control transistor, but there is another option - to include two such chips stabilizer in parallel. It should only harmonize their regimes current work, so he through both the chip was the same.
The operational amplifier operates in comparator mode. It equalizes the currents which occur in the circuit due to the voltage drop across the resistors R1 and R2. Note that these resistors is dissipated approximately 2 watts, so it is desirable to select the appropriate power.
The output of the operational amplifier controls the operation of the first chip-stabilizer, so that the currents are equalized through both ROLL chip. Resistor R6 can not put.
It performs the role of a "burden" that in the "idle" output voltage does not overstate. Operational amplifier (op amp) may be any suitable, e.g. K140UD6, K140UD7 and the like.
In the same manner may be connected in parallel, and any other circuit stabilizers from the series ROLL or imported analogues.
Perhaps scheme with additional powerful control transistor in many ways seem easier and preferable.
In the article the task was to provide only the information available, as an option. Furthermore, in this embodiment, all stored switching function ROLL chips, in particular, protection against short-circuit at the output.