Analog Design

What is Analog Design?

Analog design is the process of creating advanced circuits that operate on continuous signals instead of discrete ones. Digital electronics are discrete because they communicate using ones and zeros – analog circuits function by transmitting continuous voltage or current as a signaling method. Typically, we use an analog circuit to turn the signal into a digital one that is processed on a microcontroller or another type of processor.

These circuits comprise resistors, capacitors, diodes, inductors, transistors, and operational amplifiers. However, today’s analog circuit design may involve using microcontrollers or other intelligent, active components.

Before the integrated circuit, electronics were built from discrete electronic devices such as resistors, transistors, diodes, etc. However, the digital circuit revolution allowed computing to grow from almost nothing to being as ubiquitous as it is today. Electronic devices are in nearly everything we build, but we must consider what it takes to make them work.

Your microprocessor only knows how to process ones or zeros, which it then performs operations on to make the calculations you want. However, what if you’re going to interface with the natural world? How would you take sound and turn it into a discrete signal? This is where analog circuits come into play.

With analog design, engineers build circuits that can work with continuous signals using sophisticated tools for that function.

 

Why is analog design important?

We could not create a working circuit without understanding analog design. The foundation of digital circuits is still the flow of electricity and the fundamental forces that act on this electricity. Electricity isn't digital and doesn’t work that way in real circuits. We still need analog design knowledge to ensure our digital circuits work as expected. Furthermore, we cannot interface with the world without understanding analog electronics. Natural phenomena such as light and sound waves are continuous signals instead of discrete ones. The electromagnetic spectrum is a continuous signal that varies based on frequency and other factors.

So, analog design is the foundation of ALL electronics. You can only build digital electronics by understanding how the analog electrical signal moves inside your digital circuit. However, there are specific areas where analog design is even more important, such as:

RF and Wireless Designs

The entire electromagnetic spectrum is analog. These are a series of continuous waves that differ in frequency. When you speak on your cell phone, the connection between your device and the tower is analog. Without analog design, we couldn’t create most wireless communication devices.

Power Circuits

As you might remember, we use AC in our power distribution and DC in our devices. Therefore, a process where analog circuits turn that power into DC is necessary. These circuits are essential for us to get most electric devices to work. Power circuits also rely on analog design in other areas, but we will talk about them later.

Sensors

Creating a device that reads a physical value is typically done with an analog circuit. This is because a digital circuit would only know how to output on or off. Instead of a thermometer, imagine a device that only told you hot or cold; there would be no temperature measurement happening. In many different areas, it is necessary to read precise physical values from the world. These circuits allow you to calculate measurements and turn them into useful information as precisely as possible.

How does analog design work?

Since analog design is needed in every type of electronic device, it is valuable to understand how the process enables you to build the best circuit possible. Most analog designers create many types of analog ICs. These include:

  • Amplifiers
  • Audio amplifiers
  • Data converters
  • Power management
  • Temperature sensors
  • Clock and timing

Analog circuits are much harder to design because there are no abstractions. You are interfacing directly with the natural world; your goal is to do that as accurately as possible. You must also consider noise and other electromagnetic interference because those issues can cause problems in the circuit. Noise, when introduced into an analog signal, can affect the integrity of its value. A slight deviation can cause a significantly different outcome in an analog processing module. It is vital to keep analog circuits clear from high-speed signals as well.

Digital design is more straightforward because your focus is only on manipulating the ones and zeros to obtain functionality from the circuit. There is much more abstraction when working with digital circuits than analog ones. Analog design works differently depending on the circuit. Let's look at some examples:

How Does Analog Design in Power Applications Work?

Power supplies are an essential part of any electrical engineering project. A machine running on electricity will likely need a power supply. Therefore, power supplies are usually one of the first places to consider in analog design. A power supply takes the alternate current from your wall and turns it into the direct current that your other electronic circuits use. I'm sure you remember college physics and the graph of an alternate current. Your analog circuit needs to convert this wave into a straight line. The best analog designers can turn AC current into smoother DC that will perform well regardless of spikes or fluctuations.

Analog Design in Audio

As noted, sound waves are also continuous. Therefore, all devices that produce or take sound as an input must convert an analog signal into a digital one. As audio engineering is valuable in entertainment, business, and generally all areas of life, it is crucial to understand analog design to create circuits that produce an accurate output that is as crisp and clear as possible.

Analog in Communications

In general, the internet and digital communications have built the modern world. Communication devices are analog because they work on the electromagnetic spectrum. Even important civil and military devices like radars work using the electromagnetic spectrum. These devices work by converting a real-world analog signal to a digital one that can then be processed and sent to another device. For example, an analog circuit processes your voice when you call someone. It turns your voice into a digital signal that is then sent to the receiver to be decoded and turned back into an analog sound to which the person on the other end of the phone call can listen. The same is true for all communication devices. For radar, analog returns must be analyzed and turned into a digital signal before being displayed to the radar operator.

In general, most devices today are a combination of analog and digital. However, you usually take in analog signals from the outside world and turn them into digital signals you can represent on the screen.

Analog design with Cadence

The good news is that analog design is easier than it used to be. Cadence offers a complete suite of tools that helps you design, layout, and simulate your analog circuits. Cadence tools can help you with custom IC, RF design flows, and other processes you must go through when creating your analog projects.

Cadence offers:

  • Virtuoso Studio – Offers broad custom/analog design software for RF, systems, photonics, mixed-signal, and advanced heterogeneous designs
    • Virtuoso Schematic Editor - Allows you to visualize even the most complicated custom IC designs and provides the starting point for most analog design
    • Virtuoso ADE Suite - Verify, analyze, and explore your analog design against your stated goals to help you stay on track
    • Virtuoso Layout Suite - Shortens the process of custom IC layouts and creating digital, mixed-signal, and analog designs down to the block level
    • Virtuoso InDesign DRC – Increases productivity in implementation and physical verification. It also does instantaneous signoff DRC checks with native integration of the Pegasus Verification System in Virtuoso Studio
  • Cadence provides several different solutions for addressing specific analog circuit design needs

Other Cadence tools are well integrated to complete analog verification of your design specification, pre- and post-layout when layout parasitics must be considered for accurate analog design.

  • Spectre Circuit Simulator - Provides accurate SPICE simulation and comprehensive analyses for robust design and verification of analog, RFIC, memory, and mixed-signal designs. It is deeply integrated into the Virtuoso ADE Suite.
  • Pegasus Verification System - Enables customers to complete full-chip signoff DRC on both traditional planar and advanced-node designs
  • Quantus Extraction Solution - As a single, unified tool, supporting both cell-level and transistor-level extractions during design implementation and signoff.

Start simplifying your analog design with Cadence today.