Digital Stethoscope Amplifier Explained
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- Опубликовано: 14 окт 2024
- An example of Digital Stethoscope Amplifier is explained in this circuit analysis video. The Stethoscope's microphone picks up patient's signal (for example heart beats or bowel movements). This analog signal is initially weak and noisy and hence it needs to be properly enhanced and amplified (aka signal conditional or signal interfacing). An example of the microphone signal amplification and noise removal is explained in this video using dual op amp stage amplifier and bandpass filter. In order to achieve proper signal conditioning, very low drift (or zero drift) FET-input op amps from Texas Instruments or Analog Devices are highly recommended to make sure op amp input voltage drift is limited to sub micro volt level with minimal thermal drift. This video explains How the circuit works and computes the overall voltage transfer function of the Stethoscope Amplifier for the microphone signal at input.
You offer an appropriate consideration of the circuit. You explain it very well; kudos! What type of pickup sensor is typically used for this application? If it is some type of audio microphone, then it bears mentioning that the type of microphone used would greatly influence the design of the circuit... For example, an Electret microphone uses a different circuit than a Dynamic microphone. At least that is what I know of audio microphone circuit design. Admittedly, I am no expert. I am not fault finding, here. It is just a thought for anyone considering actually building your design. Thank you so much for sharing your expertise, time and effort to teach us.
@t1d100 Thank you! My pleasure! You have a good practical point and I appreciate sharing your thoughts. I am assuming an Electret microphone in this Stethoscope Amplifier Circuit example. More Sensors Circuits Videos are posted in ruclips.net/p/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt video playlist.
This is interesting! Thank you for sharing
You are welcome! Glad that you liked this Digital Stethoscope Amplifier video. I hope you also like the Electric Guitar Amplifier to XLR Audio Signal ruclips.net/video/X4y8cwZdGEk/видео.html
and EKG ECG Amplifier with Right Leg Drive Explained ruclips.net/video/1c7KGXPs4do/видео.html
Thank you.
Very nice example. Why are those 2 stages with different upper frequency? Does it have some practical advantage? And what is the 27pF input capacitor for?
Thank you! Good questions. This design method is not unique. There are many alternative techniques and methods to design these amplifiers. One reason for the higher bandwidth of the second amplifier stage is avoiding further magnitude drop at the upper passband edge of the first stage. As for the 27pf capacitor, it provides more stability while also shorting very high frequency noise components at the input of the circuit. More amplifier circuit videos are posted in ruclips.net/p/PLrwXF7N522y5679YAO-lFrNVYqV9XMNTr circuits playlist. I hope you like them as well.
I really like your content. If only I had this kind of detailed explanation of circuits as a young teenager over 50 years ago, when the only access to information I had was from expensive magazines and the local library reference section, which I could not borrow from and could not take home to study. Only one question for you, why is this called a digital stethoscope amplifier when it is just a simple analog amplifier? Is this just marketing BS by the manufacturer?
Glad that you like my videos and circuit design examples. I understand, I had similar limitations back in my early days as well. Regarding your question, this is not a marketing theme. A digital stethoscope requires initial analog signal conditioning (filtering and amplification) before analog to digital conversion for further digital post processing. In case you are interested here are additional practical examples:
Electric Guitar Amplifier to XLR Audio Signal ruclips.net/video/X4y8cwZdGEk/видео.html
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I hope these circuit videos are interesting as well.
This is great stuff thank you !!
Would you consider providing analysis on circuits based on viewers requests ?
My pleasure! Glad that you like this video. Sure, please share circuits you have in mind, and if it's within my expertise I'll analyze it in a video. The list of existing 200+ circuits videos are posted in ruclips.net/p/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt videos playlist. Thanks.
what is the benefit of the 27pf capacitor ?
Good question, it provides more stability while also short very high frequency noise components at the input of the circuit. See more sensor circuit examples in this video collection ruclips.net/p/PLrwXF7N522y7Ut9bm8TXAOhIWqL__FGlj. Thanks for watching.
A Digital Stethoscope Amplifier is explained in this video. Here are a few more Sensors and Circuits videos:
EKG ECG Amplifier with Right Leg Drive Explained ruclips.net/video/1c7KGXPs4do/видео.html
Electric Guitar Amplifier to XLR Audio Signal ruclips.net/video/X4y8cwZdGEk/видео.html
Bridge Audio Amplifier Explained ruclips.net/video/EDpu6urAtHA/видео.html
Thermocouple Amplifier with Cold Junction Compensation Explained ruclips.net/video/-BsDLBI166U/видео.html
Op Amp Amplifier with Electronic Gain Control ruclips.net/video/NoNgQpbj77Y/видео.html
Push-Pull Power Amplifier with Darlington Transistors ruclips.net/video/866MYibo8yE/видео.html
VCA Electronic Gain Control (Part 1): Voltage-Controlled Attenuator Overview ruclips.net/video/cFzYZsPEtP0/видео.html
Electronic Gain Control for Op Amp Amplifier ruclips.net/video/NoNgQpbj77Y/видео.html
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See more Sensors & Instrumentation Amplifiers videos in ruclips.net/p/PLrwXF7N522y4c7c-8KBjrwd7IyaZfWxyt Circuits playlist.
Didnt you miss a pole in the origin somewhere?
Thanks for watching and your interest in this circuit. As briefly explained in 3:40 and onward, there are large DC decoupling capacitors at the input of the circuit that effectively kills DC indicating that we dominantly have a zero at origin in the circuit. Here is another audio amplifier example: Electric Guitar Amplifier to XLR Audio Signal ruclips.net/video/X4y8cwZdGEk/видео.html that might be interesting and helpful.