The L7818CV is a positive fixed linear voltage regulator from STMicroelectronics, delivering a regulated 18 V output at up to 1.5 A continuous current. It is a single-regulator device in the standard TO-220-3 through-hole package, supplied in tube packaging.
Regulation and protection
Ripple rejection is specified at 53 dB at 120 Hz, which is the standard rectified line frequency — this means the output ripple from a full-wave rectifier is attenuated by a factor of roughly 450, keeping the DC rail clean for downstream analog or digital loads. Maximum dropout voltage is 2 V at 1 A output (typical), so the input rail must stay at least 2 V above the 18 V output under full load to maintain regulation. The quiescent current is 8 mA, typical for a 1.5 A LDO of this generation. Built-in over-temperature and short-circuit protection allow the regulator to survive output faults and thermal overload without external clamping diodes. Operating temperature range is 0°C to 125°C, covering commercial and industrial ambient environments but not extended automotive or military temperature extremes.
The TO-220-3 package (supplier device package TO-220) is a through-hole, tab-mount form factor. The metal tab is internally connected to the output pin — it should be soldered to a copper plane or heatsink for thermal management at 1.5 A continuous load. The mounting hole suits a standard TO-220 heatsink clip or screw. Maximum input voltage is 35 V, so the regulator can be fed from a 24 VDC rail or a rectified 24 VAC transformer with margin for line transients.