Puzzle 31 of 100

An AND-OR-INVERT gate

Goal

Make Y low while A and B are both high, or while C is high. Build it as one gate.

Die: 13 by 15 squares
Layers: Metal, Polysilicon, Contact, N active, P active, N well
Inputs: A, B, C
Output: Y
Supply: VDD
Ground: GND

New in this puzzle

Compound gates

One gate can compute the inverse of a whole expression of AND and OR. In the N strip, inputs joined by AND are in series and inputs joined by OR are side by side; the P strip uses the opposite arrangement.

One node, two contacts

A strip can pass the same node twice, with other transistors between the two places. Give the node a contact at each place and join the contacts with metal.

Guide

Paint N active silicon across the three gate lines, just above GND.
Place the outlined contacts and join the two end contacts to GND. A and B now form a series pair, and C forms a path of its own beside them.
Paint the N well and a strip of P active silicon across the gate lines under VDD.
Place the outlined contacts, and join the one between A and B to VDD. A and B now pull the contacts on either side of them high.
Paint the outlined metal under the P strip to join the contacts at the two ends of the A and B pair. They become one node, which C connects to the contact at the right end.
Join the P contact at the right end to the N contact between B and C, and run the line to Y.

Hint

Put the N transistors of A and B in series between Y and GND, and the N transistor of C beside them. The P transistors use the opposite arrangement: A and B side by side, in series with C. The P node between the pair and C appears at both ends of the pair, so join its two contacts with metal.

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 31, An AND-OR-INVERT 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 31, An AND-OR-INVERT 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 31, An AND-OR-INVERT 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

Metal63 squares
Polysilicon39 squares
Contact14 squares
N active7 squares
P active14 squares
N well44 squares
Input padA, B, C
Output padY
Supply padVDD
Ground padGND
Squares you draw, change, or erase67 squares

About the drawing

The drawing uses 114 of the die's 195 squares.
Part of the drawing is in place when the puzzle opens. To finish it, paint 49 empty squares and change 18 drawn squares.
It forms 6 transistors: 3 N transistors and 3 P transistors. Each one is a place where polysilicon crosses active silicon.
14 contacts join metal to the polysilicon or active silicon under it.

Starting drawing for puzzle 31, An AND-OR-INVERT gate, on a numbered grid. — The drawing when the puzzle opens. The dashed outline marks the squares the solution changes.