Circuits: VLSI

Puzzle 23 of 100

AND from NAND

Goal

Make Y high only while A and B are both high. The NAND gate is drawn: add an inverter after it.

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

Go to the solution

New in this puzzle

Gates in a row

The output of one gate can drive the inputs of the next. A NAND gate followed by an inverter is an AND gate, because the inverter undoes the inversion.

Guide

  1. Draw an inverter in the outlined place, sharing the rails with the NAND gate.
  2. Join the NAND output to the inverter's polysilicon line, and the inverter's output to Y.

Hint

Draw an inverter to the right of the NAND gate and join the NAND output to the inverter's polysilicon line. The two gates can share the VDD and GND rails.

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 23, AND from NAND, 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 23, AND from NAND, 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 23, AND from NAND, 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

  • Metal90 squares
  • Polysilicon33 squares
  • Contact17 squares
  • N active13 squares
  • P active26 squares
  • N well68 squares
  • Input padA, B
  • Output padY
  • Supply padVDD
  • Ground padGND
  • Squares you draw, change, or erase42 squares

About the drawing

  • The drawing uses 165 of the die's 228 squares.
  • Part of the drawing is in place when the puzzle opens. To finish it, paint 39 empty squares and change 3 drawn squares.
  • It forms 6 transistors: 3 N transistors and 3 P transistors. Each one is a place where polysilicon crosses active silicon.
  • 17 contacts join metal to the polysilicon or active silicon under it.
Starting drawing for puzzle 23, AND from NAND, on a numbered grid.
The drawing when the puzzle opens. The dashed outline marks the squares the solution changes.