Micrologic 1960 Design Logic Gate Layout Schematic
# Design a Logic Gate as a Layout, Not Just a Schematic: Turning a Circuit Diagram Into Geometry
## 1. Why a Resistor Value Is No Longer a Part You Order, It Is a Shape You Draw
This step takes a logic gate's circuit schematic — a handful of transistors and resistors wired together to perform one Boolean function — and converts it into a physical floorplan on silicon, where every component this project has so far treated as a single device now has to coexist with several others on the same substrate, sharing the same diffusions, the same oxide, and the same interconnect layer this project's 1959 series established. The most immediate consequence is that a resistor stops being a discrete part with a catalog value and becomes a shape: a diffused strip of the same doped silicon this project has used for a base or an emitter, whose resistance is set entirely by its geometry rather than by anything ordered from a supplier.
where $R_{\text{sheet}}$ is the sheet resistance of the diffused layer — a property of the dopant concentration and depth this project has controlled since 1954 — and $L$ and $W$ the length and width of the resistor strip as drawn in the layout. A circuit designer no longer specifies a resistance value and expects a part to arrive; this step's designer specifies a length-to-width ratio and trusts that the same diffusion already characterized for transistor junctions will deliver a predictable resistance from pure geometry.
## 2. Real Diagram: A Floorplan, Not a Single Device's Cross-Section
Every cross-section this project has drawn since 1954 showed one device from the side. This step's layout is a top view of several devices and their connecting resistors, arranged on one piece of silicon to realize a specific logic function — the first drawing in this project's history where the relative *position* of multiple components, not just any one component's own geometry, is the thing being designed.
## 3. Why Every Earlier Series Only Ever Had to Design One Device at a Time
The 1954, 1956, 1958, and 1959 series each documented a process for building a single transistor, and even where that transistor eventually sat on a wafer among many identical copies — as in 1957's batch processing — every copy was the same device repeated, not several different components cooperating to perform a function. This step is the first in this project's history where the thing being designed is a *circuit*, and the layout decisions it makes — where each transistor sits, how long a resistor strip runs, how interconnect threads between them — have no equivalent in any earlier series, because no earlier series ever needed more than one kind of answer to "what goes here."
Step 1 does not fabricate anything; it decides, on paper, what this series' silicon will have to become — the first time in this project that a single piece of silicon has been asked to be more than one component's home.