Puzzle 22 of 100

A NOR gate

Goal

Make Y high only while A and B are both low.

Die: 13 by 12 squares
Layers: Metal, Polysilicon, Contact, N active, P active, N well
Inputs: A, B
Output: Y
Supply: VDD
Ground: GND

New in this puzzle

Series and parallel swap

In a CMOS gate the P transistors are arranged the opposite way to the N transistors. Where the N pair is in series, the P pair is side by side, and the reverse.

Guide

Draw two P transistors in series between VDD and the output, one gate for each input.
Draw two N transistors side by side, each between the output and GND.
Join the P and N outputs to Y, and bring A and B to their gates.

Hint

A NOR gate swaps the arrangement of a NAND gate: the P transistors are in series between VDD and Y, and the N transistors are side by side between Y and GND. B arrives from the right side of the die.

Solution

This is the game's reference drawing for the puzzle. It meets the goal and passes the design rules. Other drawings can pass as well.

Top View of the solved die for puzzle 22, A NOR gate, with the Side View below it. — Top View of the solved die, captured from the game. Paths that carry a high level at the moment shown are lit. The Side View below cuts through the row between the dashed lines.

The game window in Isometric View with the solved die for puzzle 22, A NOR gate, the guide, and the scope. — The whole game window in Isometric View. The scope on the right compares each output with its target band, and the message above it confirms that the drawing passes.

Solution drawing for puzzle 22, A NOR gate, drawn on a numbered grid with every layer in its game color and pattern. — The solution on the grid. Squares are numbered from the top left corner, so you can count them. The dashed outline marks the squares you draw, change, or erase; the rest is drawn when the puzzle opens.

Legend

Metal54 squares
Polysilicon22 squares
Contact9 squares
N active9 squares
P active18 squares
N well48 squares
Input padA, B
Output padY
Supply padVDD
Ground padGND
Squares you draw, change, or erase85 squares

About the drawing

The drawing uses 111 of the die's 156 squares.
Part of the drawing is in place when the puzzle opens. To finish it, paint 85 empty squares.
It forms 4 transistors: 2 N transistors and 2 P transistors. Each one is a place where polysilicon crosses active silicon.
9 contacts join metal to the polysilicon or active silicon under it.

Starting drawing for puzzle 22, A NOR gate, on a numbered grid. — The drawing when the puzzle opens. The dashed outline marks the squares the solution changes.