In the night light circuit, a solar cell with a peak output voltage of about 5 V is used to recharge the Li-Ion cell with a voltage of 3.7 V. When exposed to external daylight, the voltage supplied by ...

The NAND gate is a circuit that outputs '0' when both inputs are '1', and '0' otherwise, so if you arrange the NAND gate as follows, the Invert circuit is completed.