Sallen Key Low Pass Filter, bandpass filter

[Maglatron]

I'm struggling with it!

 

[Maglatron]

do you filter and then put an envelope circuit to then output to the LM3914

 

[Maglatron]

is this good or bad thinking

 

[Maglatron]

I'm finding it difficult to find strait answers on google, anyway I have much more project time to work on my things so that's really good at least two hours per week on mondays maybe an hour extra in the mid week!!

 

[bertus]

hello,

the simplest envelope detector is a diode with a capacitor and a resistor:

Envelope detector - Wikipedia

en.m.wikipedia.org

bertus

 

[Maglatron]

is the order of the block diagram in post #243 correct

how do I go about designing the envelope circuit I realise that it can be done with a diode with a capacitor and a resistor

I also want to ability to use a jack instead of a mic via a chip as stated in post #29

I'll just use this because it's precision and I'm all about precision and will enjoy putting together, for the opamps in the diagram can I use the TL074CN's that I already have, cheers. One thing I do want to know it how can you set the circuit up for reference ground comming from the buffer circuit, Please colud someone modify the image so that I can utilise REF ground please

 

[Maglatron]

so I can use the TL074CN for the pre-amp, I can the TL074CN the for filters, I can use the TL074CN for buffer circuit with the reference stage and that, I want to know if i can use the TL074CN in the - precision full-wave detector yay or nay? I also want to edit the circuit for it to run off the same REF gnd so I think the resistors and capacitors need swapping out! and would appreciate some help with that please

 

[Maglatron]

so alore

1. Type:
   • TL074CN: Quad JFET-input operational amplifier.
   • LF353: Dual JFET-input operational amplifier.
2. Pin Configuration:
   • TL074CN: 14-pin DIP (Dual In-line Package).
   • LF353: 8-pin DIP.
3. Power Supply Voltage:
   • TL074CN: Typically operates from ±4V to ±18V.
   • LF353: Typically operates from ±4V to ±18V.
4. Input Bias Current:
   • TL074CN: 30 pA (picoamperes) maximum.
   • LF353: 50 pA maximum.
5. Input Offset Voltage:
   • TL074CN: 3 mV maximum.
   • LF353: 3 mV maximum.
6. Common-Mode Rejection Ratio (CMRR):
   • TL074CN: 70 dB minimum.
   • LF353: 70 dB minimum.
7. Open-Loop Gain:
   • TL074CN: 100 dB minimum.
   • LF353: 100 dB minimum.
8. Slew Rate:
   • TL074CN: 13 V/µs typical.
   • LF353: 13 V/µs typical.
9. Temperature Range:
   • Both typically cover the industrial temperature range of -40°C to 85°C.
10. Noise Characteristics:
    • TL074CN: Not specified (depends on the specific model).
    • LF353: 18 nV/√Hz typical (input referred).

I think that it should be ok to use the TL074CH in place of the LF353!

 

[Maglatron]

how do I change the circuit to accomodate for the input bias current

Input Bias Current:

• TL074CN: 30 pA (picoamperes) maximum.
• LF353: 50 pA maximum.

these types of questions, I can't just search for on a search engine!

 

[Maglatron]

is this good or bad thinking

from post #243

 

[Maglatron]

I want to modify the envelope detector circuit to run on virtual ground. I might need to swap out resistors and capacitors.
For this precision full wave peak detector, I need to alter the resistors and capacitors for +VS 12Volt -VS 0Volt, for reference ground and I'll be using a TL074CN for the operational amplifiers. Anyone think they can give it a crack?? the AD8031U1M will also be replaced with an operational amplifier in side of the TL074CN chip as will the LF535! 1st picture, EXAMPLE, 2nd picture is the one I want altering to have REF gnd (virtual ground), and 3rd picture is when The filter circuit has been changed to single supply, using a virtual ground reference: thanks in advance!!!

 

[Harald Kapp]

is the order of the block diagram in post #243 correct

yes

 

[Maglatron]

Cool, that is good!

 

[Maglatron]

can you help with post #254 please? cheers

 

[Maglatron]

I noticed that when the filters have a reference voltage the last two filters out of the four swap around the values of the resistors and capacitors (in filterwizard). Because they are the same but not neccessarly the same order, is it that its the same outcome? do I just connect the grounds to the reference and use all of the same values of resistors and caps?

 

[Maglatron]

Why are the stages (A,B,C,D) not in order? all the stages stay the same!

 

[Maglatron]

Hello,

No, one buffer is likely enough for several filters.

Bertus

how many max?

 

[Maglatron]

Would this work?!? with all the op-amp TL074CN

 

[Maglatron]

and where do the bypass filters go

 

[Maglatron]

I think that I pretty much have it sussed now, just need the last "Yes, that would work!" for my confidence