Depending on their location, linear voltage regulators are arranged traditionally into two sub-groups: series and shunt (or parallel) regulators. In practical circuits, series regulators. particularly the popular integrated types in the 78xx family, are normally used since these give good regulation and allow a reasonable output current. Nevertheless, good shunt regulators are also becoming available, for example. Texas Instruments’ “Irpe TIA31. The commercial version of this, the TIA31C, offers excellent temperature stability and very low dynamic impedance (see table). Although shunt regulators usually function in the same way as a zener diode, the TI1431C offers a facility that no zener diode does: the zener voltage may be set anywhere between 2.5 V and 36 V with the aid of two fixed resistors. To function properly, the device needs a cathode current of not less than 1 mA. The voltage across the IC is tlaenUca, = 2.5(1+R2/R1). if the values of R2 and R3 are not too high, the current through this reference network is negligible pA). 1..()Possible application of the device compact 5 V power supply is shown in the diagram.
SOME TECHNICAL DATA
Cathode voltage,Ucat 2.5 V-36 V
Cathode current,Icat 150 mA
Power dissipation (1 m.A. min) 775 mW (at 25 C)
Dynamic impedance 0.5 Ω (typical 0.2 Ω)
Temperature coefficient 30 ppm K-1