Analog Signal Attenuation

David Cooper's picture

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Joined: Dec 27, 2019

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Analog Signal Attenuation
December 28, 2019 - 12:05am

<p>I have a circuit with two stages.&nbsp; The first stage generates an analog signal varying in the range of 0V to 5V.&nbsp; The output impedence of this stage is about 100 ohms.&nbsp; This is fed into a second stage with an input impedence of about 8K ohms.&nbsp; What I'd like to be able to do is add a state in the middle such that the signal voltage is cut in half.&nbsp; That is, the signal is linarly mapped onto a 0V to 2.5V range.&nbsp; Initially, I thought I need to design this intermediate stage with an input and output impedence matching that of the existing two stages.&nbsp; That is my intermediate stage would have input and output impedences of 8K and 100 ohms.&nbsp; Naively I suppose I could just put a pot in there as a voltage divider and the user can adjust appropriately to their needs, so to speak.&nbsp; Is that the right approach?&nbsp; If that is the right approach, then how would I go about reasoning the value of the resistors in the divider (i.e. a good value for the center tapped pot).&nbsp; Does this make sense?&nbsp; I'm open to any approach, including those involving semicondutors.</p>

John_Kripto's picture

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Joined: Aug 11, 2018

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use a buffer circuit with potential divider
December 30, 2019 - 5:31pm

From what I understood, you need a middile stage that would convert 0-5V to 0 to 2.5V without disturbing the existing impedace level in the circuit. One way I could think of is to use a buffer circuit after the 1st stage. This buffer circuit will have very high input impedace and very low output impedance it hence will not disturb your 1st stage of 3rd stage working.

Now to convert the 0-5V to 0-2.5V you can use a voltage diver circuit. If you want to calculate the values, then you can use the https://circuitdigest.com/calculators/voltage-divider-calculator. Your input voltage will be 5V and your output voltage will be 2.5V, enter any value for R1 (like 1K) and calculate the value for R2

 

Hope this helps