Cadence-1: Introduction to Cadence Virtuoso | CMOS Inverter| Tutorial for creating Schematic

Introduction to Cadence Simulator Tool

Overview of the Tool

• Rafal introduces the Cadence simulator tool, emphasizing its utility for creating electronic circuit schematics.

• The interface consists of three main windows: Library Manager, Overview, and Log, which displays errors related to added files.

Library Management

• Users can add technology nodes (e.g., TSMC 180nm, TSMC 65nm) through the Library Path Editor in the log window.

• To add a new library (e.g., UMC 130nm), users must specify a name and path for it.

Available Components

• The tool provides various categories of components including RF devices, BJTs, diodes, capacitors, and MOSFETs.

• Ideal components like current sources and resistors are available for initial design phases before replacing them with practical components.

Understanding Circuit Design Process

Functionality of Schematic Tools

• Cadence Virtuoso is part of a suite that includes tools for schematic design; similar tools exist under Mentor Graphics (now Siemens).

• These tools allow users to drag-and-drop components into designs while automatically generating SPICE code in the background.

SPICE Code Generation

• An example illustrates how conventional SPICE code is written for circuits using resistors and voltage sources.

• A link to a detailed video on SPICE code is provided for further learning.

Creating a New Library in Virtuoso

Steps to Create a New Library

• Users initiate library creation by selecting "File" then "New Library," specifying a name and associating it with an existing technology node.

• After choosing TSMC 65nm as the technology node, users create their new library which will utilize this PDK.

Designing Schematics

• Users can create new cell views within their libraries by naming them appropriately (e.g., "first") and selecting schematic type.

• The user interface allows instantiation of components; shortcuts like pressing 'i' facilitate component selection from libraries.

Component Instantiation Example

• For designing an inverter circuit, users need one NMOS and one PMOS transistor; they can select these directly from the symbol browser.

How to Instantiate a PMOS and Connect Circuit Components

Instantiating a PMOS

• To instantiate a PMOS, press the 'i' button and select 'p' for p-channel or browse for the PMOS symbol. The arrow direction on the symbol indicates its type.

Connecting Circuit Points

• Use wires to connect circuit points; shortcuts include pressing 'w' to create narrow or wide wires with left mouse clicks.

Ground and Voltage Connections

• The source of NMOS is grounded while the source of PMOS connects to VDD. Use analog labels to assign voltage sources by pressing 'i' and selecting VDC.

• Assign ground by typing 'g' in an unlocked library, then click on the ground symbol. You can add multiple grounds as needed.

Setting Voltage Parameters

• To set a specific voltage (e.g., 1.8V for PMOS), click on the component, press 'q', adjust parameters, and apply changes.

Creating Input/Output Pins

• Create input pins by clicking "create pin" and setting direction as input; similarly, create output pins with direction set as output.

Connecting Wires and Managing Components

Wire Connections

• Connect common drain outputs with input at common gate using wires; moving components can be done by holding left-click.

Copying Components

• Select components using left-click, copy them with 'c', and place them where needed within your schematic design.

Naming Nets for Clarity

• Right-click to add net names (e.g., VDD), which helps in connecting similar nodes across different parts of the circuit efficiently.

Checking Schematic Integrity

Zooming and Shortcuts

• Use "zoom to fit" or press 'f' to adjust viewable area; learn shortcuts like 'i' for instantiation, 'w' for wire creation, and others for efficient navigation.

Parameter Adjustments

• Modify parameters such as width (W) or length (L); use keyboard shortcuts like ‘q’ for parameter settings directly related to selected instances.

Finalizing Your Schematic Design

Checking Errors

• After completing your schematic, check it using Shift + X; this will reveal any warnings that need addressing before finalization.

Resolving Warnings

• Common issues include unconnected body terminals in MOSFET devices; ensure NMOS body is connected to ground while PMOS body connects to VDD.

By following these steps systematically, you can effectively design circuits involving PMOS transistors while ensuring all connections are correctly established.

How to Use a Resistor in Circuit Design

Instantiating and Manipulating Components

• To instantiate a resistor, access the unlock library and click on the symbol. This allows you to add components to your schematic.

• Rotating components can be done by pressing the middle button of your mouse (usually the scroll wheel). Alternatively, pressing 'R' while using the mouse also facilitates rotation.

• To create a mirror image of a component, select it and press 'Shift + R'. This action will flip the component horizontally.

• Flipping components can be achieved by pressing 'F', which provides another method for adjusting component orientation.

Summary of Learning Outcomes

• In this introduction video, viewers learned how to add new libraries and PDK into their workspace, as well as how to instantiate various components and connect them using keyboard shortcuts.

• The next video will focus on simulating the schematic created in this session, building upon these foundational skills.