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Wednesday, October 6, 2010

IC 723 Voltage Regulators

Figure shows the basic circuit of an IC 723 voltage regulator. This IC has a voltage reference source, an error amplifier, a series pass transistor, and a current limiting tran­sistor all contained in one small package. The device can be connected to operate as a positive or negative voltage regulator with an output voltage ranging from 2 V to 37 V, and output current levels upto 150 m A. The maximum supply voltage is 40 V, and the line and load regulations are each specified as 0.01%.

Figure shows an IC 723 connected to operate as a positive voltage regulator. The output voltage can be set to any value between approximately 7 V (reference voltage) and 37 V by appropriate selection of resistors R1 and R2. A potentiometer may be included between R1 and R2, of course, to make the voltage adjustable. An external transistor may be Darlington connected to Q1 (as shown in earlier post) to handle large load current. The broken lines in the figure shows connections for simple (non-foldback) current limiting. (Foldback current limiting can also be used with IC 723). A regulator output voltage less than the 7 V reference level can be obtained by using a voltage divider across the reference source [terminals 6 and 7 in earlier figure]. The potentially divided reference voltage is then connected to terminal 5.
It is important to note that the supply voltage, at the lowest point on the ripple waveform, should be at least 3 V greater than the output of the regulator and greater than VREF; otherwise a high-amplitude output ripple may occur.