First, a quick thanks in advance. I am looking to have my process verified - I used the example numbers from the book to guide myself. I'm doing homework involving band-pass filters and I'm not confident I understand the voltage drop across a pass-band filter. I'm working with RC high pass and low pass filters in series, not sallen-key filters.

The example in the book's section on band-pass filters has a high pass RC filter in series with a low pass RC filter. C-high = 1.5nF, R-high = 1kΩ; R-low = 40kΩ, C-low = 4pF.

Low cut-off frequency = 106.1kHz

High cut-off frequency = 994.72kHz.

The book's analysis at ~500kHz shows a Vo ≈ 0.9Vi.

In my analysis, I assumed Vi = 1V for simplicity, and obtained Vo = 0.874V.

First, I figured out the reactance of both capacitors:

Xc high = (2*pi*500000*1.5*10^(-9))^-1 = 212.2Ω

Xc low = (2*pi*500000*4*10^(-12))^-1 = 79.6kΩ

Next, since the diagram shows a high-pass filter as the first stage, I went through the Av for it first.

Av high = (1+ (Xc/R)^2)^(-0.5)

Av high = (1 + (212.2Ω/1000Ω)^2)^(-0.5) = 0.97822

Then, the low pass filter.

Av low = (1 + (R/Xc)^2)^(-0.5)

Av low = (1 + (40kΩ/79.6kΩ)^2)^(-0.5) = 0.89348

Multiplying these numbers together gives the Av for the entire bandpass filter, Av = 0.874Vin.

Anyone care to comment? Reassurance would be very very nice at this point. Sorry for the MSPaint circuit drawing, I don't have access to MultiSim right now.

The example in the book's section on band-pass filters has a high pass RC filter in series with a low pass RC filter. C-high = 1.5nF, R-high = 1kΩ; R-low = 40kΩ, C-low = 4pF.

Low cut-off frequency = 106.1kHz

High cut-off frequency = 994.72kHz.

The book's analysis at ~500kHz shows a Vo ≈ 0.9Vi.

In my analysis, I assumed Vi = 1V for simplicity, and obtained Vo = 0.874V.

First, I figured out the reactance of both capacitors:

Xc high = (2*pi*500000*1.5*10^(-9))^-1 = 212.2Ω

Xc low = (2*pi*500000*4*10^(-12))^-1 = 79.6kΩ

Next, since the diagram shows a high-pass filter as the first stage, I went through the Av for it first.

Av high = (1+ (Xc/R)^2)^(-0.5)

Av high = (1 + (212.2Ω/1000Ω)^2)^(-0.5) = 0.97822

Then, the low pass filter.

Av low = (1 + (R/Xc)^2)^(-0.5)

Av low = (1 + (40kΩ/79.6kΩ)^2)^(-0.5) = 0.89348

Multiplying these numbers together gives the Av for the entire bandpass filter, Av = 0.874Vin.

Anyone care to comment? Reassurance would be very very nice at this point. Sorry for the MSPaint circuit drawing, I don't have access to MultiSim right now.

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