Puzzle 18 of 100

A slow fall

Goal

Make Y fall about four times more slowly than it rises, as the target shows. The inverter is drawn.

Die: 15 by 12 squares
Layers: Metal, Polysilicon, Contact, N active, P active, N well
Input: A
Output: Y
Supply: VDD
Ground: GND

New in this puzzle

Channel length

A longer channel passes less current. Length is the number of squares across the gate from source to drain, so a gate line four squares wide makes a weak transistor.

Hint

Widen the polysilicon over the N active silicon so that the gate is four squares across, with N active silicon on both sides of it. The P transistor stays as it is.

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 18, A slow fall, 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 18, A slow fall, 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 18, A slow fall, 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

Metal55 squares
Polysilicon20 squares
Contact7 squares
N active8 squares
P active10 squares
N well32 squares
Input padA
Output padY
Supply padVDD
Ground padGND
Squares you draw, change, or erase12 squares

About the drawing

The drawing uses 98 of the die's 180 squares.
Part of the drawing is in place when the puzzle opens. To finish it, paint 9 empty squares and change 3 drawn squares.
It forms 2 transistors: 1 N transistor and 1 P transistor. Each one is a place where polysilicon crosses active silicon.
7 contacts join metal to the polysilicon or active silicon under it.

Starting drawing for puzzle 18, A slow fall, on a numbered grid. — The drawing when the puzzle opens. The dashed outline marks the squares the solution changes.