Top | Lac781p Schematic

The output side of the LAC781P is where the regulation happens. The internal bandgap reference compares a fraction of Vout to a stable voltage. External capacitors C2 and C3 are critical:

Some top schematics also include a reverse protection diode (1N4001) from Vout to Vin, and a small LED + resistor on the output as a power indicator. lac781p schematic top

The input pin receives unregulated DC voltage (typically 2-3V above the output voltage). Internally, the input first passes through a start-up biasing network. This section powers the internal reference and provides base current to the pass transistor during initial power-on. The output side of the LAC781P is where

Although not drawn explicitly in a top-level schematic, the LAC781P contains: Some top schematics also include a reverse protection

The top schematic should note that a heatsink is required for loads >500mA.