symmetrical power supply - 0 to ± 18 V; 0 to ± 1 A

symmetrical power supply elektor december 1983 0 to ± 18 V; 0 to ± 1 A Figure 1. The three-ter- minal integrated, adjust- able regulator type LM 317 operates as a series regu- lator. The required output voltage is obtained by adding voltage divider R 1/R2. The minimum load current is set to 10 mA by means of R 1. The specification of a symmetrical mains power supply must include the provision of two precise, identical voltages (one positive, the other negative) which can be set with ONE potentiometer. It must be possible to set the lowest voltage to 0 V. And, perhaps most important of all, the unit must have adjustable current-limiting, which on over- load reduces or switches off BOTH cur- rents. We have not often used the LM 317 (posi- 1 tive) and LM 337 (negative) adjustable voltage regulators in our designs and a few words about these devices may, therefore, not come amiss. They are very easy to use and require only two external resistors to set the output voltage and an outp...