Inexpensive miniature transformers normally provide one or two secondary voltages, which is sufficient for generating a set of positive and negative supply volt-ages, such as are needed for operational amplifier circuits. But what can you do if you need an additional voltage that is higher than either of the supply voltages (such as a tuning voltage for a receiver?). This circuit shows a simple solution to this problem, and it certainly can be extended to suit other applications. Using a 2×15-V transformer, it generates positive 24-V and 12-V supply voltages and a negative 12-V supply voltage. Circuit diagram : Simple Triple Power Supply Circuit diagram The little trick for generating the +24-V output consists of using IC1 to create a virtual ground. This is based on a well-known circuit with a voltage divider formed by two equal-valued resistors, which divide the voltage Ub across the rectifier from approximately 40 V down to 20 V. This Ub/2 potential is buffered by an opamp, whi...