Let's experiment with ADALM2000! Op-amp low-frequency noise evaluation

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Introduction

In the previous article, we introduced Analog Devices' Active Learning Module "ADALM2000" as a "portable laboratory" and explained its versatility and easy setup method.

Let's experiment with ADALM2000! A portable laboratoryADALM2000

Now, let's take a deeper look at the ADALM2000 and try a more practical experiment. The subject of this experiment is the Analog Devices demo board "EVAL-KW4502Z".

In this article, we will introduce in detail the specific methods and benefits of practical circuit evaluation by linking the ADALM2000 and EVAL-KW4502Z. We hope that this series will help you improve your electronic circuit evaluation skills and make debugging more efficient.

What is EVAL-KW4502Z?

The EVAL-KW4502Z is a demonstration board that enables evaluation of the low-frequency noise of operational amplifiers. It is designed to quickly measure the low-frequency noise from 0.1Hz to 10Hz of operational amplifiers with different characteristics such as low power consumption, low noise, and zero drift.

EVAL-KW4502Z Evaluation Board | Analog Devices

The ADALM2000 not only supplies low-voltage power supplies such as the ±5 V required by the EVAL-KW4502Z, but also uses its oscilloscope function to directly visualize and analyze in detail the low-frequency noise output from the operational amplifier under test. Low-frequency noise evaluation, which previously required bulky equipment, can now be achieved simply by combining the palm-sized ADALM2000 with a dedicated evaluation board, allowing high-quality evaluation to be performed anywhere.

Opening the EVAL-KW4502Z

Let's take a look at the contents of the EVAL-KW4502Z kit. The kit is very simple and contains the following:

EVAL-KW4502Z evaluation board
2-Pin Mini Jumper Short Circuit Cap

As shown in the photo, the EVAL-KW4502Z board is compact enough to fit perfectly into the palm-sized ADALM2000 (11.5cm x 7cm). The 2-pin mini jumper short circuit cap is attached in the location shown. It's necessary for switching the op-amp, so be careful not to lose it!

Connecting to ADALM2000

Next, connect it to the ADALM2000. Integration is easy: simply connect the EVAL-KW4502Z to the pin header on the top of the ADALM2000 main module, matching the pin layout.

Download the Scopy configuration file in advance

To perform this demo, we will first download the Scopy configuration file (.ini file) provided by Analog Devices.

Access the URL below and download "hosc_scopy_config_files.zip". We will use the configuration file "Noise Demo Oscilloscope Config.ini" contained in the zip file later.

Low Frequency Noise KWIK Lecture + Lab [Analog Devices Wiki]

When you load this configuration file in Scopy, the oscilloscope's time axis will be automatically set to 625ms/div, the voltage axis to 200mV/div, and the power supply will be automatically set to ± 5V and enabled.

In the next section, we will look at the specific steps for measuring low-frequency noise using this evaluation environment.

Visualizing noise signals with the Scopy oscilloscope function

Connect your PC and ADALM2000 with a USB-A to USB-micro-B cable and launch Scopy.

*This time, we will not use the jumper cables and pin headers that come with the ADALM2000.

Scopy Software setup, including PC Regarding the connection with Previous article Please see.

In Scopy, first select the ADALM2000 module, then click the “Connect” button to connect.

Scopy Above, first ADALM2000 Select the module, then Connect” button to connect.
Once the connection is complete, ADALM2000 Main unit LED1 will flash.

Next, select "Load" and load the "Noise Demo Oscilloscope Config.ini" that you downloaded earlier.

The following screen will appear. The time and voltage axes of the oscilloscope have been automatically set.

Also, when you select Power Supply, you can see that it is automatically set to ± 5V.

Switch the jumper to select the type of op-amp being evaluated.

This kit allows you to evaluate the low frequency noise of three types of operational amplifiers.

Low power op amp: LT1782 → Set the jumper to "LOW POWER"
Low noise bipolar op amp: ADA4077 → Set the jumper to "LOW NOISE"
Low noise zero drift op amp: ADA4522 → Set the jumper to "ZERO-DRIFT"

First, set the jumper to LOW POWER and measure the low frequency noise. Note that the filter time constant is 10 seconds. Please note that after enabling the power and setting the jumper, it may take up to one minute for the filter to stabilize.

Evaluate the low power op amp LT1782 by setting the jumper to "LOW POWER"

Let's measure!

The explanation of the preparations has gotten a little long, but it's finally time to take the measurements.

Select "Oscilloscope" → "Run".

After waiting a few seconds, the following waveform will be displayed. Next, use the Measure function to see numerically how much low-frequency noise is being emitted.

After waiting a few seconds, a waveform like this will appear.
Next, we will use the Measure function to see the amount of low-frequency noise being emitted.

If you turn on "Display All", you can read the Peak-peak value and AC RMS value.

"Display All" ON If you change it to Peak-peak and AC RMS When I performed the following, the values were 1.372V, 203.889mV The value obtained was:
These values are output-referred noises, and to calculate input-referred noise, the total gain of the measurement system is 10⁶ You need to divide by .
That is, the input-referred noise is Peak-peak By value 1.372 μ Vpp, RMS By value 204Vrms It has become.

This is how we were able to visualize and measure the low frequency noise of the LT1782. It was that easy!

So what about the ADA4077?

Now that we have measured the low frequency noise of the LT1782, let's try measuring the low frequency noise of the ADA4077. Switch the jumper to "LOW NOISE".

Evaluating the ADA4077 low-noise bipolar op amp with the jumper set to "LOW NOISE"

If we measure low frequency noise using the same procedure as before, the noise is clearly smaller on the graph.
Looking at the numbers, we can see that it has been reduced to about 1/5, as you would expect from a low-noise amplifier.

What about the ADA4522?!

Finally, we switched the jumper to "ZERO-DRIFT" and evaluated the ADA4522.
As its name"zero drift"suggests, this amplifier produces almost no offset drift even when used for long periods of time, and is also said to have extremely excellent low-frequency noise performance.

How low noise is it actually?
How effective is Zero Drift?

I'm sure you're curious, but I'll end this article here. Get your hands on the ADALM2000 and EVAL-KW4502Z and see for yourself how excellent the ADA4522 is!

Summary

What did you think.

This time, we combined ADALM2000 and EVAL-KW4502Z to actually measure the low-frequency noise of an op amp.

"I want to experience the numbers on the data sheet in person."

"I want to compare the differences in operational amplifiers by looking at waveforms."

This was the perfect tool and experiment for such people.
I think it's a very valuable experience to be able to see with your own eyes evaluations that previously required large measuring instruments, using just this compact piece of equipment on your desk.

Now, let's start experimenting using the "Portable Laboratory ADALM2000"!!!

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