Unlock the Secrets of Vintage Op Amp Noise with Spice Models

When it comes to simulating the characteristics of vintage operational amplifiers (op amps),one crucial aspect that cannot be overlooked is the noise generated by these analog devices. Op amp noise can significantly impact the performance of analog circuits, and understanding and accurately simulating this noise plays a vital role in circuit design and analysis.

The Quest for Vintage Perfection

Vintage op amps have garnered a cult following in the audio engineering community due to their unique sonic characteristics. Audio enthusiasts swear by the warmth and richness these op amps bring to their gear, making them sought-after components for audio gear restoration and DIY projects.

However, recreating the genuine vintage sound is not as simple as inserting a vintage op amp into a circuit. The noise profile of these op amps plays a crucial role in the overall audio quality they deliver, making it essential to accurately simulate this noise during the design phase.

Slopes and Levels: Spice Models to Simulate Vintage Op-Amp Noise

by Burkhard Vogel(Kindle Edition)

5 out of 5

Language	:	English
File size	:	76343 KB
Print length	:	363 pages

FREE

Spice Models: A Powerful Tool for Noise Simulation

Fortunately, spice modeling comes to the rescue when it comes to simulating vintage op amp noise. SPICE (Simulation Program with Integrated Circuit Emphasis) models are mathematical representations of real-world components that allow engineers to simulate and analyze circuit behavior.

By using spice models, engineers can recreate the noise characteristics of vintage op amps in virtual environments. This enables them to analyze the impact of noise on circuit performance, fine-tune the circuit design, and optimize overall system performance.

Understanding Op Amp Noise

Before diving into how to simulate op amp noise using spice models, it's crucial to understand the different types of noise encountered in op amps:

1. Thermal Noise

Thermal noise, also known as Johnson-Nyquist noise, arises due to the random motion of charged particles within a conductor at any finite temperature. This noise is commonly encountered in all electronic components and can be accurately modeled using the appropriate mathematical equations.

2. Shot Noise

Shot noise occurs due to the discrete nature of the electric charge. This noise is encountered in semiconductor devices such as diodes, where individual electrons and holes traverse the junction, causing random fluctuations in the current flow.

3. Flicker Noise

Flicker noise, also known as 1/f noise or pink noise, is a low-frequency noise component that increases as the frequency decreases. It is primarily caused by defects and imperfections within the semiconductor material and can significantly affect the performance of low-frequency circuits.

4. Burst Noise

Burst noise, also called popcorn noise, is characterized by intermittent amplitude fluctuations. It is commonly encountered in devices operating at high frequencies and can result from various sources such as surface defects or trapping of charge carriers.

Steps to Simulate Vintage Op Amp Noise with Spice Models

Simulating vintage op amp noise using spice models involves a few steps:

1. Identify the Vintage Op Amp

First, it is essential to identify the specific vintage op amp you wish to simulate. Each op amp has its unique noise characteristics, so accurately determining the model is crucial.

2. Obtain the Spice Model

Next, you need to obtain the spice model for the vintage op amp. Spice models are typically provided by the manufacturer and can be downloaded from their website or other reliable sources.

3. Implement the Spice Model

Once you have the spice model, you can implement it in your circuit simulation software or spice simulator. Most software applications allow users to import external spice models and seamlessly integrate them into their circuit designs.

4. Configure Noise Sources

To accurately simulate vintage op amp noise, it is crucial to configure the appropriate noise sources in your circuit simulation. Depending on the spice simulator you are using, you can typically add noise sources directly from the predefined components or use the corresponding mathematical equations to model the noise.

5. Run the Simulation

After configuring the noise sources, run the simulation to analyze the noise characteristics of the vintage op amp. Pay close attention to how the noise affects the overall performance of the circuit and make necessary adjustments to optimize the design.

Benefits of Simulating Vintage Op Amp Noise

Simulating vintage op amp noise using spice models offers several benefits:

• Design Optimization: By accurately simulating op amp noise, engineers can identify potential noise-related issues early on and optimize circuit designs accordingly.
• Cost Reduction: Simulating noise characteristics allows engineers to avoid expensive trial-and-error approaches, reducing development costs and time to market.
• Performance Enhancement: Understanding how noise affects circuit performance enables engineers to fine-tune their designs and achieve superior audio quality.
• Educational Value: Simulating op amp noise provides a valuable learning experience, allowing engineers to deepen their understanding of noise mechanisms and their impact on circuit operation.

Simulating vintage op amp noise using spice models unlocks a world of possibilities in audio circuit design. By accurately modeling and analyzing the noise characteristics of these analog gems, engineers can optimize circuit performance, achieve vintage-like sounds, and embark on a rewarding journey of audio engineering perfection.

Slopes and Levels: Spice Models to Simulate Vintage Op-Amp Noise

by Burkhard Vogel(Kindle Edition)

5 out of 5

Language	:	English
File size	:	76343 KB
Print length	:	363 pages

FREE

This book features an extensive index and all Mathcad worksheets.

Vinyl is back, tubes/valves are back, on the high-end field SMD-free analog amplification surpasses digitalized chains, and top microphone manufacturers still set on good old op-amps or on fully discrete BJT, FET, and/or tube-driven amplifiers. There is only one problem that is not satisfyingly well solved by the manufacturers: It is the noise production of the active components and the useful reflection in simulation tools, in tables or graphs of the datasheets/data books.

Nowadays, mostly surrounded by many digital helping tools, it makes sense using them—also by analog aficionados. It saves cost and time simulating first before spending money. Presented in this book the software tool LTSpice which is the free software solution from Linear Technology (today Analog Devices) that could also be used by full analog lovers to simulate the noise production of their amplifier design. All we need is the right creation approach to develop simulation models for the active components. Inter alia this is already done for tubes and BJTs in the 2nd editions of my “How to Gain Gain” and “Balanced Phono-Amps” books. For op-amps, the missing approaches are presented in the book on hand.

It cannot be denied that mathematical software like Mathcad is extremely helpful to find the right equations for graphically presented noise curves which we can find in the literature. Nevertheless, it also works well with other types of math software to fulfill the parameter needs of the here presented modeling approaches for the input referred voltage and current noise of—not only—excellent sounding vintage op-amps, applicable in the audio range from 1 Hz to 100 kHz.