# Band-pass filter

How do I ensure that the output voltage is at least 20% below the input voltage in this band-pass filter if the given resistor value is 100 Ω and the input voltage is 2 V?

• With that circuit? You don't. Filters don't work that way or with those specifications. A resistor divider will do that though. Commented Dec 31, 2022 at 6:47
• Shorting the output will certainly ensure that the output is at least 20% below. <-- this is what happens when you don't give enough information in the question. I mention this because in engineering, the devil is always in the details and EEs have to wade through plenty of detail so, if you are inclined to be an engineer, my comment should be seen as helpful. In other words, you need to provide more details in your question to establish unambiguously what you want. Commented Dec 31, 2022 at 11:37

A simple voltage divider will work but will broaden the band pass.

simulate this circuit – Schematic created using CircuitLab

As per GodJihyo's comment $$\R_2\$$ should be $$\400\Omega\$$ for 20% below.

• They said 20% below the input. Making R2 400 ohms will satisfy the requirement and affect the bandwidth less. Commented Dec 31, 2022 at 15:21
• Thanks @GodJihyo. Added a correction. Commented Dec 31, 2022 at 17:33
• To preserve the bandwidth and meet the gain requirements, make R1 = 125 ohms, R2 = 500 ohms.
– qrk
Commented Dec 31, 2022 at 17:49

How do I ensure that the output voltage is at least 20% below the input voltage in this band-pass filter

This circuit largely preserves the Q-factor of the resonant point but may consume a lot of power in the potential divider formed by the 4 Ω and 1 Ω resistor: -