# Articles by Steve Sandler

## Measuring High Output Voltage Regulator Noise

In this power-electronics article, we focus on noise measurement of 48 V range voltage regulators (VRs), up to a maximum of 65 V. We propose a noise measurement setup and examine this method.

## How Can You Measure a HUGE Inductance with DC Bias?

Steve Sandler was recently asked to measure a 25 mH inductor. Read on to find out what happened next.

## The Ultimate Power Rail Noise Measurement

Do I really need to use a power rail probe to measure ripple and noise? Power rail probes are single ended, so does that mean I can only monitor one power rail at a time? Are there other, more affordable options available? In this blog post, Steve Sandler answers to these questions and more.

## Determining FPGA Dynamic Load Current

In this Extreme Measurement story, the goal was to determine the dynamic current of the FPGA by measuring the AC current in an external VRM using a transformation of the PCB S-parameters and the simultaneous measurement of the AC voltages across the PDN.

## How Fast is the Switching Speed of a GaN Switch?

Check out this latest installment in the Extreme Measurements Blog that covers the measurement challenges for GaN switches.

## Measuring the Bulk Dielectric Constant (Dk) on a Microstrip with a TDR

If you have designed a controlled impedance transmission line based on a PCB stack-up, how do you know if the PCB fabrication house or another vendor built your stack-up to meet your controlled impedance specification?

## How Can You Determine the Turns Ratio of a Power Transformer in a Sealed DC-DC Module?

I do not know if there was a legitimate reason for this request, but I was once asked to determine the turns ratio of a power transformer inside a sealed, DC-DC converter module.  In any case, there is not much usable information since the module is sealed, but we can apply a simple trick. Check out this latest installment in Extreme Measurements.

This extreme measurement seems more impossible than difficult.  The traditional stability assessment method for voltage regulators is the Bode plot.  Access to the control loop is required and a small signal is injected into the control loop, usually via a resistor, placed at the top of the voltage sense divider. Without access to this voltage divider, there isn’t a place to inject a signal into the control loop, and therefore the Bode plot is seemingly impossible…

## Cable Shield Resistance Issue in a 2-port Impedance Measurement

In this Extreme Measurement Example, see how measurements were used to resolve the shield resistance issue, where the authors redesigned the PCB to clear the DUT contact, but also identified alternate solutions in the event they could not wait for a new PCB.