Stability

Covers loop stability analysis and design, including Bode plots, phase/gain margin, control loop behaviour, and techniques for ensuring stable operation in power systems.

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Picotest Expands Line of PSRR Line Injectors Adding Inductor and Input Impedance Testing

We have released a new line injector for PSRR (power supply rejection ratio), DC-biased inductor, and DC-DC converter input impedance testing. The J2121A is…
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Article
Bode Plots are Overrated

Control loop stability is critically important. But whether your focus is on power supply design, power integrity, or mixed-signal power system design, the Bode…
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Article
Accurately measure ceramic capacitors by extending VNA range

Ceramic capacitors play an oversized role in circuit performance as a major contributor to voltage regulator control loop stability and power delivery network (PDN)…
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Article
Introduction to NISM – Non-Invasive Stability Measurement with Steve Sandler

In this video, Steve Sandler shows how to measure control loop stability using the Bode 100 VNA via Output Impedance. This test can be…
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Video
Killing the Bode Plot

Many new linear devices, including voltage references, voltage regulators and opamps have internal feedback loops, prohibiting traditional bode plots. Yet, the assessment of stability…
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Article
Flat Impedance in Voltage Regulator Modules

Today’s high speed systems require clean power under challenging conditions. Extremely fast current transients and high voltage stability require carefully designed power delivery. In…
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Article
Impedance measurements stabilize op-amp buffers

The unity-gain op amp (operational amplifier) buffer circuit is routinely used to transform high-impedance inputs into low-impedance outputs. ADC (analog-to-digital converter) voltage references are…
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Article
Impedance measurements make a difference at DesignCon

What do clock jitter, EMI, control loop stability, SPICE modeling, rogue waves and the ripeness of fruit have in common? Do you need to…
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Article
PICOTEST NEWSLETTER 1/2015

Picotest Announces Transmission Line Probes Solve Loading/Cable & Load Step Issues Picotest’s 1 and 2 Port 50 ohm transmission line probes are now available. These…
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Video
PICOTEST NEWSLETTER 11/2014

Picotest Announces Low Cost Full Featured POWER SUPPLY 15% Educational Discount Outperforms the Keysight E3632A at half the price! The P961xA Series of programmable, single output,…
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Article
Keysight E5061B VNA Gains Non-Invasive Stability Measurements

NISM software is now available. Bringing the unique non-invasive stability test to the Keysight E5061B vector network analyzer. The software add-on, available now for…
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Article
Three Stability Assessment Methods Every Engineer Should Know About

Many engineers are familiar with the Bode plot as an effective stability assessment method. However, some authors suggest and even teach that the Bode…
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Article
SPICE models need correlation to measurements

Many SPICE models are available online that were created by IC and semiconductor manufacturers. Unfortunately, availability doesn’t necessarily equal usability. The majority of these…
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Article
Software Enables Accurate Stability Test, Improves Non-Invasive Phase Margin Measurement Accuracy

Many articles and application notes have come out in recent years discussing the assessment of stability without access to the control loop, since the…
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Article
PCB characteristics affect PDN performance

The basic design rules for power distribution networks (PDN) teach us that the best performance is obtained from a uniform, frequency independent (or flat)…
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Article
Five Things Every Engineer Should Know About Bode Plots

The Bode plot is recognized for its simplicity and the simple asymptotic approach makes the method useful for both design and assessment of power…
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Article
Non-Invasively Assess Your Multiple-Loop LDO’s Stability

Some low-dropout regulators (LDOs) use multiple feedback loops to improve output voltage transient response. In many of these cases, some or all of the…
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Article
Troubleshooting Distributed Power Systems: The Switch (Part 6 of the ongoing series.)

System and power converter issues are frequently related to a converter’s switching characteristics, which are most easily observed at the switching node. In this…
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Video
How To Verify Control Loop Design

The non-invasive stability assessment is a method that uses an output impedance measurement to accurately determine stability without access to the control loop. The…
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Article
How to Solve 8 of 10 Design Issues

The vast majority of design issues are directly or indirectly attributable to control loop stability. The most common offenders: Linear regulators Voltage references Op-amps…
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Article
Troubleshooting Distributed Power Systems: Impedance Is the Critical Measurement (Part 2 of the ongoing video series.)

Whether your goal is to optimize system performance or to troubleshoot issues in distributed power systems, impedance measurement is an indispensable tool. That’s because…
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Video
Troubleshooting Distributed Power Systems: Why Stability Matters (Part 1 of the ongoing video series.)

Control-loop stability impacts power supply performance in multiple ways. Even if the control loop is not oscillating, poor stability—as evidenced by low phase margin—in…
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Video
FAQ #23 What Injectors do I need for PDN Measurements?

Our J2112A current injector has been the most requested product to date. It provides a very fast low current pulse, though based on a…
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Article
Assessing Point-Of-Load Regulators Using Non-Invasive Techniques

Evaluating the stability of a Point-Of-Load (“POL”) regulator can be performed using both traditional Bode plot and output impedance measurement techniques. Measuring output impedance…
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Article
FAQ #22: So how does this non-invasive measurement relate to phase margin and gain margin?

It doesn’t, at least not directly. Since stability is an assessment of the proximity of the gain vector to the singular unstable point, (1,0)…
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Article
New Injector Supports Testing of POLs

High Fidelity POL Testing with the J2112A The J2112A: Faster, Non-Invasive, and High Fidelity POL Step Load Testing Testing the step load performance of…
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Article
Exploring Bandwidth, Gain Margin and Phase Margin in Non-Invasive Measurement

SummaryAmong the most frequently asked questions regarding non-invasive stability measurement are “How do I determine the bandwidth, phase margin and gain margin from the…
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Article
Essential Test Adapters for Your Network / Impedance Analyzer

The network analyzer, sometimes referred to as a Frequency Response Analyzer (FRA) is a common piece of equipment in most of our labs today.…
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Article
When Bode Plots Fail Us

It may come as a surprise to some that a control loop’s Bode plot does not always depict the loop stability and that the…
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Article
Evaluate Feedback Stability When There’s No Test Point

It’s impossible to directly measure the stability (gain/phase) characteristics of a device if the device’s control loop lacks an access point to apply a…
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Article
Introduction to the J2110A Solid State Injector

Most of us have experience using a wideband signal injection transformer to introduce a modulation signal into our loop stability test. While a high-quality…
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Article
Extracting Bode Plots from Output Impedance

Many articles and application notes describe the extraction of phase margin, using a non-invasive technique that extracts the phase margin from an output impedance…
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Article
Stability Assessment of Fixed Regulators

There are cases where a Bode (gain?phase) plot cannot be obtained from a control loop. For example, a three terminal regulator or hybrid may…
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Article
Measuring the Output Impedance of Voltage References and Zener Diodes

In this article we examine the process of measuring a key performance characteristic, output impedance, using the Picotest J2130 DC Dias Injector and the…
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Article
Measuring the PSRR of Voltage References

In this article we detail the process of measuring a key performance characteristic of voltage references, power supply rejection ratio or “PSRR”, using the…
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Article
New Technique for Non-Invasive Testing of Regulator Stability

Output impedance is the key to testing filter and regulator phase margin, even when the control loop is inaccessible. Many voltage regulators are of…
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Article
A Simple Method to Determine ESR Requirements for Stable Regulators

A single, simple measurement is described that allows the determination of the ESR required to achieve a desired phase margin, using a particular value…
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Article
Measuring Optocouplers with the J2130 DC Bias Injector and the OMICRON Lab Bode 100 VNA

Many power supplies use optocouplers in the feedback loop. The stability and overall performance of the power supply are often dependent on the CTR…
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Article
Selecting Test Signal Injectors

A number of test signal injectors are used when evaluating the performance of power supplies and other low-frequency components with a network analyzer. Network…
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Article
Powering RF and Microwave Systems

RF/microwave design engineers faced with developing effective power circuits for a system require more complete data sheets, appropriate computer-aided simulation models, and suitable test…
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Article

Stability

Picotest Expands Line of PSRR Line Injectors Adding Inductor and Input Impedance Testing

Bode Plots are Overrated

Accurately measure ceramic capacitors by extending VNA range

Introduction to NISM – Non-Invasive Stability Measurement with Steve Sandler

Killing the Bode Plot

Flat Impedance in Voltage Regulator Modules

Impedance measurements stabilize op-amp buffers

Impedance measurements make a difference at DesignCon

PICOTEST NEWSLETTER 1/2015

PICOTEST NEWSLETTER 11/2014

Keysight E5061B VNA Gains Non-Invasive Stability Measurements

Three Stability Assessment Methods Every Engineer Should Know About

SPICE models need correlation to measurements

Software Enables Accurate Stability Test, Improves Non-Invasive Phase Margin Measurement Accuracy

PCB characteristics affect PDN performance

Five Things Every Engineer Should Know About Bode Plots

Non-Invasively Assess Your Multiple-Loop LDO’s Stability

Troubleshooting Distributed Power Systems: The Switch (Part 6 of the ongoing series.)

How To Verify Control Loop Design

How to Solve 8 of 10 Design Issues

Troubleshooting Distributed Power Systems: Impedance Is the Critical Measurement (Part 2 of the ongoing video series.)

Troubleshooting Distributed Power Systems: Why Stability Matters (Part 1 of the ongoing video series.)

FAQ #23 What Injectors do I need for PDN Measurements?

Assessing Point-Of-Load Regulators Using Non-Invasive Techniques

FAQ #22: So how does this non-invasive measurement relate to phase margin and gain margin?

New Injector Supports Testing of POLs

Exploring Bandwidth, Gain Margin and Phase Margin in Non-Invasive Measurement

Essential Test Adapters for Your Network / Impedance Analyzer

When Bode Plots Fail Us

Evaluate Feedback Stability When There’s No Test Point

Introduction to the J2110A Solid State Injector

Extracting Bode Plots from Output Impedance

Stability Assessment of Fixed Regulators

Measuring the Output Impedance of Voltage References and Zener Diodes

Measuring the PSRR of Voltage References

New Technique for Non-Invasive Testing of Regulator Stability

A Simple Method to Determine ESR Requirements for Stable Regulators

Measuring Optocouplers with the J2130 DC Bias Injector and the OMICRON Lab Bode 100 VNA

Selecting Test Signal Injectors

Powering RF and Microwave Systems