There are various ways to implement an active "voltage reducing block" at the output of a regulator that subtracts from the reference voltage to bring the output down to ground potential

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• Article «Drive LDOs To 0-V Output With Single Supply»
• Figure 1. There are various ways to implement an active "voltage reducing block" at the output of a regulator that subtracts from the reference voltage to bring the output down to ground potential
• Figure 2. For situations where the supply rail is positive and limited, a passive approach using resistors is an alternative to the active techniques from Figure 1
• Figure 3. For adjustable regulators such as the L200, a shunt regulator acts as an active voltage reducer while a potentiometer allows careful adjustment to the desired voltage value
• Figure 4. A similar approach works with the 78xx family, but requires a change in the details of the circuit topology
• Figure 5. If a negative voltage is needed, there are various common techniques to generate negative dc rails from an ac supply, including a full-wave bridge plus additional diode (a), a full-wave bridge plus negative dc-dc converter and regulato (b), a half-bridge