science

Verilog-A

Verilog-A is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Verilog-A rather than just read about it. In short: Verilog-A is an industry standard modeling language for analog circuits. It is the continuous-time subset of Verilog-AMS.

Key takeaways

Verilog-A belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Verilog-A to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Verilog-A from memory before moving on to harder problems.

Reference excerpt

Verilog-A is an industry standard modeling language for analog circuits. It is the continuous-time subset of Verilog-AMS. A few commercial applications may export MEMS designs in Verilog-A format.

History Verilog-A was created to standardize the Spectre behavioral language in the face of competition from VHDL (an IEEE standard), which was absorbing analog capability from other languages (e.g. MAST). Open Verilog International (OVI, the body that originally standardized Verilog) agreed to support the standardization, provided that it was part of a plan to create Verilog-AMS—a single language covering both analog and digital design. Verilog-A was an all-analog subset of Verilog-AMS that was the project's first phase. There was considerable delay between the first Verilog-A language reference manual and the full Verilog-AMS, and in that time Verilog moved to the IEEE, leaving Verilog-AMS behind at Accellera.

Standard availability Verilog-A standard does not exist stand-alone - it is part of the complete Verilog-AMS standard. Its LRM is available at the Accellera website. Future work will likely leverage the new net-type capabilities in SystemVerilog. Built-in types like "wreal" in Verilog-AMS will become user-defined types in SystemVerilog more in line with the VHDL methodology.

Compatibility with the C programming language A subset of Verilog-A can be translated automatically to the C programming language using the Automatic Device Model Synthesizer (ADMS). This feature is used for example to translate the BSIM Verilog-A transistor models, which are no longer released in C, for use in simulators like ngspice.

Code example This first example gives a first demonstration of modeling in Verilog-A:

This Verilog-AMS example implements an ideal diode, by defining the current through the branch (a,c) depending on voltage at branch terminals (a), (c), and the ambient temperature of the simulated circuit:

For a simple DC voltage source, the branch voltage is set to the constant (DC) value:

A sine voltage generator can use the built-in sin() function:

Worked examples

Example 1 — a first encounter with Verilog-A

Start with the simplest possible case. Write down what Verilog-A claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Verilog-A before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Verilog-A ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Verilog-A

In research: Verilog-A appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Verilog-A in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Verilog-A is common in secondary-school and first-year university syllabi. It links to neighbouring topics Hardware description languages, so understanding it makes those chapters shorter.
In everyday life: Look for Verilog-A outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Verilog-A in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Verilog-A means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Verilog-A out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Verilog-A in simple terms?

Verilog-A is an industry standard modeling language for analog circuits. It is the continuous-time subset of Verilog-AMS.

Why does Verilog-A matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Verilog-A?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Verilog-A.