Deboo INtegrator ( in Low Pass Filter)

mokong

Joined Oct 14, 2011
6
Hi,

I am trying to use a deboo integrator on my low pass filter because I am using a single supply for my op amp for my project. Can anyone know how to implement the deboo integrator on my circuit to avoid clipping and without affecting the frequency response. Thanks for any help.

here is the link for my circuit, frequency response, and AC transient:

circuit: http://imageshack.us/photo/my-images/94/des3q.png/

AC: http://imageshack.us/photo/my-images/257/wave3w.png/

Frequency: http://imageshack.us/photo/my-images/855/fre3.png/

hgmjr

Joined Jan 28, 2005
9,027
Greetings mokong,

Be patient, it takes some time for an interested member to formulate a response to your question.

hgmjr

SgtWookie

Joined Jul 17, 2007
22,230
The LMx24 series is not an RRIO opamp (rail-to-rail input-output). It's common mode range includes ground, but it is limited to about Vcc - 1.5v. You are seeing clipping at about Vcc - 1v, which is better than what the specifications call for, your actual mileage will probably be worse.

If you want to eliminate the clipping, then do at least one of:
1) Reduce the amplitude of your input signal voltage to keep it within the common mode range of the opamp.
2) Increase Vcc to 6.5v or higher; at least 7.5v suggested, and increase the offset of your input signal by 0.5v.
3) Replace the LM124 with an opamp that is RRIO.

Audioguru

Joined Dec 20, 2007
11,248
The circuit has a single supply and all the opamps have their inputs biased at ground so the output is a rectified signal, not as shown.
The input must be biased at about half the supply voltage.

SgtWookie

Joined Jul 17, 2007
22,230
The circuit has a single supply and all the opamps have their inputs biased at ground so the output is a rectified signal, not as shown.
No.

The OP's input is a sine wave with an amplitude of 2.4v and an offset of 2.5v.

They didn't show the 2.5v offset in the simulation, but it must exist, or otherwise they would not get any output.

I more or less replicated their output in LTSpice; except the LM324 model I used is a bit closer to what the specs call for; the output was clipped at ~ 3.6v instead of ~4v.

I used an opamp symbol with the inverting and noninverting inputs swapped; unless you happen to have a symbol called LM324a, LTSpice will complain.

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Audioguru

Joined Dec 20, 2007
11,248
The OP's input is a sine wave with an amplitude of 2.4v and an offset of 2.5v.

They didn't show the 2.5V offset in the simulation, but it must exist, or otherwise they would not get any output.
I mentioned the missing input offset because it is not shown.

They didn't show the 2.5v offset in the simulation, but it must exist, or otherwise they would not get any output.
The circuit will produce a clipped output with the negative-going parts missing (rectified).

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