Low-drop regulator II

If a stable 5-V direct voltage is to be deIived from an already low supply voltage, the 4805 from SGSThomson is probably the most suitable regulator IC available at present. The popular 7805 does not work so well with supplies lower than about 8 V. The 4805, on the other hand, needs an input voltage that is only about 0.5 V higher than its output voltage. Its data sheets state that its output voltage remains stable so lang as the input voltage does not drop below 5.7 V. That voltage, by the way, is the worst-case voltage when the output current is 400 mA. In practice, therefore, theregulatornormally works flne with input voltage as low as 5.4 V.