Why do digital oscilloscopes appear noisier than traditional analog oscilloscopes?
Dave busts the myth that digital scopes are noiser than analog scopes, and demonstrates what inherent advantages digital scopes can have over analog scopes in terms of true waveform capture. And also why your analog scope may be hiding important signal detail from you.
Demonstrations of how memory depth, analog bandwidth, averaging, and intensity graded displays can all effect the signal detail you see on your digital oscilloscope.
And how long exposure camera shots on analog oscilloscopes can reveal detail you can’t see with your eyes.
EEVblog #601 – Why Digital Oscilloscopes Appear Noisy – [Link]
Dave explains what the ripple and noise specifications on a power supply is and how to measure it using different methods on both analog and digital oscilloscopes. From bad techniques through to good, showing the effect of each one. Traps for young players aplenty in this one. How do you detect common mode noise issues and ensure that the signal you are measuring is really coming from your device under test?
EEVblog #594 – How To Measure Power Supply Ripple & Noise – [Link]
Publitek European Editors :
The low-dropout regulator (LDO) has long been the choice for buck voltage conversion not only where cost is an issue but where noise performance is critical.
The brainchild of Linear Technology co-founder Robert Dobkin, conceived when he worked at National Semiconductor, the core architecture of the regulator is very simple but effective. Dobkin took a fixed-ratio voltage regulator and adapted it so that its output could be adjusted using a voltage divider on the output.¹
In the classic linear regulator, a transistor acts as half of a potential divider. Its output voltage is to control a feedback circuit that has control over the transistor’s gate in the case of a MOSFET, which is normally the case for an LDO regulator. The constant control via feedback over gate voltage provides a stable output voltage at a level set by the reference circuitry. Because of the use of a voltage divider structure, the linear regulator can produce only a voltage that is lower than that of the input. Older regulator circuits could experience a drop of 2 V or more. LDOs were devised to provide easier control over the output voltage and to constrain this dropout voltage to less than 2 V.
Linear Regulators Drive Noise Down – [Link]
Gerard Fonte writes:
My client, a small manufacturer, was having a noise problem with a new batch of 1500V-dc supplies.
It had been a while since the company manufactured this product. The original engineer was long gone, and the only documentation was a schematic. The approach was a straightforward closed-loop design. An op amp controlled an oscillator that used a step-up transformer to create the high voltage, which the system rectified and filtered into dc. A small part of the output voltage fed back into the inverting input of the op amp as an error signal to adjust the oscillator frequency when necessary. The noninverting input was grounded.
Tracing down a noise problem – an interesting story – [Link]
Ams has introduced the AS3421 and AS3422 single chip devices for active noise cancellation (ANC). Featuring integrated speaker drivers, the new devices make it easier to implement ANC in Bluetooth wireless headsets, headphones and earpieces. The ANC circuitry processes external noise sensed by a microphone embedded in the headset and generate a noise-cancelling signal, while amplifying the desired audio signal with very low distortion.
Low power consumption and long battery life are particularly important requirements in wireless headsets, and the all-analogue design of the new chips is more efficient than DSP-based (digital) speaker drivers. The devices draw just 7 mA at 1.5 V in stereo ANC mode, and less than 1 µA in quiescent mode. They also implement an ultra-low power ANC bypass mode when the user selects the playback-only function. The new devices additionally provide differential stereo line inputs to match differential line outputs from typical Bluetooth-based headset systems. [via]
Active Noise Cancellation on a Chip – [Link]
It’s time for a lecture. I’ve been spending a lot of time creating a DIY dlectrocardiogram and it produces fairly noisy signals. I’ve spent some time and effort researching the best ways to clean-up these signals, and the results are incredibly useful! Therefore, I’ve decided to lightly document these results in a blog entry.
Here’s an example of my magic! I take a noisy recording and turn it into a beautiful trace. See the example figure with the blue traces. How is this possible? Well I’ll explain it for you. Mostly, it boils down to eliminating excess high-frequency sine waves which are in the original recording due to electromagnetic noise. A major source of noise can be from the alternating current passing through wires traveling through the walls of your house or building. My original ECG circuit was highly susceptible to this kind of interference, but my improved ECG circuit eliminates most of this noise. However, noise is still in the trace (see the figure to the left), and it needed to be removed.
Signal Filtering with Python – [Link]
There are many times where you would like to “stabilize” an input signal so that you don’t see the input value “jumping” so much. This is specially true on the MilliVolt Signal range, where nearby noise present can disturb the original signal. In this case, you always have the option of buying some kind of signal conditioner, which handles the filtering function of the raw signal. However, there are many times where the noise problem presents itself after the system is built, in which case a simple software solution is preferable to mitigate the problem.
Simple Software Filter – [Link]
System-level hardware designers pay careful attention to selecting the right analog signal path ICs for their specific applications. Each IC needs “clean” power but often, power management is the last part of a system design. As many designers know, power supply design affects the analog signal integrity which, ultimately, impacts overall system performance.
National Semiconductor’s broad portfolio of low-noise, low dropout (LDO) regulators preserve signal fidelity in the analog signal path over a wide range of input voltages and output currents. National’s portfolio of low-noise LDOs provide maximum Power Supply Rejection Ratio (PSRR) and low output voltage noise for low-power, space-constrained applications. In contrast to switching regulators which induce a voltage ripple and other high frequency voltage spikes in their output, an LDO’s PSRR filters out unwanted noise.
Low Dropout Regulators Deliver Quiet Power for Noise-Sensitive Circuits – [Link]
This project is a small hand held device that allows you to create real-time noise loops with a metallic effect. It is using a microcontroller to create the noise loops and has three controls, tempo, sound and write. In the link below find instructions to build your own crazy looper. Schematics and source code is available. There is also the option to buy a kit.
Crazy Looper – [Link]