Timeline for Converting two cascaded first-order high-pass filters circuit to a second-order high-pass filter using Sallen-key configuration
Current License: CC BY-SA 4.0
7 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jul 23, 2022 at 6:24 | comment | added | a concerned citizen |
(When using @, the names must not contain spaces. Use it with @<TAB> to cycle between the available names. if none comes out then there is no need for @).
|
|
| Jul 22, 2022 at 17:21 | comment | added | a concerned citizen | @G0tBlackOps Sounds like a new question but, in short, the same as before: you combine the two 1st order into a 2nd order. You won't have one \$\omega^2\$, you'll have \$\omega_1\omega_2\$. Q will be less than 0.5, so it will be an overdamped case. E.g. \$s/(s+2)\cdot s/(s+3)=s^2/(s^2+5s+6)\;\Rightarrow\;\omega=\sqrt6,\;Q=\sqrt6/5\$. You can also combine a lowpass and a highpass, just the same. | |
| Jul 22, 2022 at 15:02 | comment | added | Scipio | @a concerned citizen If instead of having two first order filters with identical cut frequencies i had two first order filters with different cut frequencies how would i proceed with transforming from two first order stages to a single second order stage using Sallen-key configuration? How do i find the new cut frequency and Q? | |
| Jul 22, 2022 at 15:02 | vote | accept | Scipio | ||
| Jul 22, 2022 at 13:15 | comment | added | a concerned citizen | @G0tBlackOps It's difficult to say but, if you have the transfer function all you need to do is to make a system of equations and solve them:$$\begin{cases}\dfrac{1}{R_2C_1}+\dfrac{1}{R_2C_2}&=\dfrac{\omega}{Q} \\\dfrac{1}{R_1R_2C_1C_2}&=\omega^2\end{cases}$$. If you impose \$C_{1,2}\$ then the results come out as:$$\begin{cases}R_1&=\dfrac{1}{Q\omega(C_1+C_2)} \\R_2&=\dfrac{Q(C_1+C_2)}{\omega C_1C_2}\end{cases}$$. For \$C_1=C_2=1\;\mu\text{F}\$ you get \$R_1=R_2=7763.656\;\text{k}\Omega\$. In the answer it's rounded for E96. | |
| Jul 22, 2022 at 12:46 | comment | added | Scipio | See my new edit, i think the problem was in the equations used for the resistors. Perhaps in that document they're not right? | |
| Jul 22, 2022 at 7:04 | history | answered | a concerned citizen | CC BY-SA 4.0 |