# band reject filter design

Discussion in 'Homework Help' started by sarjan88, Apr 23, 2011.

1. ### sarjan88 Thread Starter New Member

Joined:
Apr 23, 2011
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Design a circuit using op-amp that will reject the 60kHz power line noise and also reject high signal frequency above 800Khz. The stop-band width around the 60kHz centre frequency is 10kHz. Use a cascade of 1st order high pass and 1st order low pass filter to implement this circuit. The voltage gain at passband frequencies is 10.

As mentioned in the title, can sum1 tell me this should be a band reject or band pass filter?
i try to construct a band reject filter but the result seem like not correct.

here is my circuit using multisim
http://i325.photobucket.com/albums/k392/sarjan123/circuit.jpg
here is the result using AC analysis in decibel
http://i325.photobucket.com/albums/k392/sarjan123/result.jpg
bode plot

can sum1 help me out of this?
thanks

2. ### beenthere Retired Moderator

Joined:
Apr 20, 2004
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What part of the world do you live in? I thought that power line frequencies were either 50 Hz or 60 Hz.

3. ### Audioguru New Member

Joined:
Dec 20, 2007
9,411
888
Your V3 battery is only 0V.
All opamps are biased at 0V and with the single positive supply they become rectifiers.
With your single +10V supply all opamps should be biased at +5V, not at 0V. Or use a double-polarity supply.