Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

design an active filter 2nd order

Status
Not open for further replies.

funjoke

Member level 3
Joined
Feb 19, 2009
Messages
58
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,286
Activity points
1,772
• No ripple can exist in the output, but non-linear phase shift is allowed.
• The frequency response must be as close as possible to the ideal filter response.
• Signals of frequency 0 ~ 5 KHz are only allowed to pass through the filter with a desired gain of 4dB . Other frequencies should reduce at least 100 times of gain for every 10 times of frequency increase.
• capacitor of 0.01uF must use in the active filter design due to its high availability in the stock.
• Minimize offset error of your design


My answer:
no ripple means butterworth, 4 db means this is HPF

fc=1/2pie RC=7957OHM
Apb =4
20logApb=4
Apb-1.585

Rf=Rapb=7957 x 1.585 =12.6kohm

Apb=1+Rf/Rs
1.585=1/(12.6k/Rs)
Rs=21.54kohm


i just know this few steps .if there any mistake
 

Very very confusing !
How can you calculate resistors without knowing the circuitry ?

Just two short comments:
1.) Gain of 4 dB in the passband of the lowpass means: Ao=+1.58
2.) Factor 100 per decade means: 40 dB/Dec >>> low pass of second order.
 

How you know the Ao is 1.58 and what are the following steps ?any guidance for me in this question ?

Added after 1 minutes:

and low pass and high pass is see the Apb ,if positive value it is high pass,if negative value it is low pass.am i correct ?
 

funjoke said:
How you know the Ao is 1.58 and what are the following steps ?any guidance for me in this question ?
Added after 1 minutes:
and low pass and high pass is see the Apb ,if positive value it is high pass,if negative value it is low pass.am i correct ?

to 1.) 4 dB is equivalent to 1.58. Do you know the meaning of dB ?
to 2.) What is the source of your assumption ? It is completely nonsense. Sorry.

Recommendation: If you like to design a filter read some introductory papers resp. books before.
 

A Sallen-Key second-order filter has a Butterworth response if its two resistors are the same and its two capacitors are the same and its gain is 1.58 (+4db).
 

Welcome to: Who can guess the circuit?

We have a new winner!
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top