Sallen Key Low Pass Filter, bandpass filter

[Maglatron]

I want to know what changing the dB does
I think passband Hz is how wide the passband will be around the centre frequency
still not sure about stop band or what it does. Looking for clear concise explanation please

 

[Maglatron]

preferably from bertus I know he spends much time helping, but his help acctually helps also want to know if I can use one of the built in op-amps of the TL074 to make the buffer circuit

 

[Maglatron]

or harald kapp, kellys eye, dananak, alec_t, martaine2005 all are very good

 

[Harald Kapp]

you make no sense

I Agree and I deleted that post.

 

[Harald Kapp]

still not sure about stop band or what it does.

Passband, aas the name says it the range of frequencies that pass the filter.
Stopband,, as the name says, is the range of frequencies that do not pass the filters, that are stopped.

can use one of the built in op-amps of the TL074

Better use the TL074H (comparison).

After the filter you will have an AC signal containing the frequency componnets of (mainly) the passband. You will need to rectify and filter this AC signal to get the envelope which is what you'll want to display by the LEDs.

 

[Maglatron]

Passband, aas the name says it the range of frequencies that pass the filter.
Stopband,, as the name says, is the range of frequencies that do not pass the filters, that are stopped.


Better use the TL074H (comparison).

After the filter you will have an AC signal containing the frequency componnets of (mainly) the passband. You will need to rectify and filter this AC signal to get the envelope which is what you'll want to display by the LEDs.

I have TL074CN type, will these suffice

 

[Maglatron]

After the filter you will have an AC signal containing the frequency componnets of (mainly) the passband. You will need to rectify and filter this AC signal to get the envelope which is what you'll want to display by the LEDs.

ok so this is to make DC for the LM3914 to read, I need a little more information on how to do this but it does make sense

 

[Maglatron]

is there a tool

getting the envelope which is what you'll want to display by the LEDs.

like filterwizard

 

[Maglatron]

can't find anything on youtube about getting envelopes

 

[bertus]

Hello,

Have a look in the LM3915 datasheet I posted.
In there are several circuits for envelope/peak detection.

Bertus

 

[Maglatron]

help please spice file, or schematic, circuit design, any more infomation welcomed equations, anything else other than the wiki. will it matter that I'm using LM3914 instead, in that datasheet it says, "The simplest way to display an AC signal using the LM3915 is to apply it right to pin 5 unrectified" is this the same with the LM3914

 

[Maglatron]

can I use the peak detector schematic in conjunction with the LM3914 also can I use my TL074CN to build it? Figure 20. Precision Full-Wave Peak Detector page 13

 

[Maglatron]

I will buy the LM3915's and the TL074H's if needs be, they are cheap enough!

 

[Maglatron]

the only thing is that the TL074H do not come in dip through hole packaging and that's not ideal for me

 

[Maglatron]

can I use the TL074CH for this? and is C1 and C2 in microfarad (uF)

 

[Harald Kapp]

help please

When I search for "envelope detector" I get lots of results from the internet. Don't let us do your job. You know how to use a search engin, puit that knowledge to the test.

 

[Maglatron]

ok cheers

 

[Maglatron]

just one more quick question can I use my TL074CH for the filters, the buffer circuit and the envelope detectors?

 

[Maglatron]

the video that I'm watching is confusing me does the the rectified AC signal come after the filter to have a varying DC voltage?

After the filter you will have an AC signal containing the frequency componnets of (mainly) the passband. You will need to rectify and filter this AC signal to get the envelope which is what you'll want to display by the LEDs.

 

[Maglatron]

If the signal out of the filter is like this does the output go to the positive side of the diode and the lower rail go to ground of REFERENCE GND