Virtuix Cad has fairly large OPA library.
Located in the library block.
It is incredible convenient.
Since it will place the whole circuit as a already assembled block.
You can Tune the block to your specifications.
Cutoff and Q
Then will generate needed resistor values
according to what value capacitor you want to use.
And what the needed Q is.
Assuming you will just be using standard Q values
Bessel = .5
Butterworth = .707
it is rather painless to design filters with it.
and pointless to use external calculators.
Since Virtuix Cad already contains a calculator
and numerous assembled blocks
just use board friendly cap values from
1n to 10n
and low noise op amp friendly resistance values
from 8 to 12k
Located in the library block.
It is incredible convenient.
Since it will place the whole circuit as a already assembled block.
You can Tune the block to your specifications.
Cutoff and Q
Then will generate needed resistor values
according to what value capacitor you want to use.
And what the needed Q is.
Assuming you will just be using standard Q values
Bessel = .5
Butterworth = .707
it is rather painless to design filters with it.
and pointless to use external calculators.
Since Virtuix Cad already contains a calculator
and numerous assembled blocks
just use board friendly cap values from
1n to 10n
and low noise op amp friendly resistance values
from 8 to 12k
Correct
And since you only need .5 Q
both capacitors and resistors will be equal.
Making the circuit a bundle of fun since both resistors are equal.
It is incredibly easy to make it a adjustable filter.
Which you could also predict with Virtuix Cad.
Using a common Dual Gang 10k potentiometer
Minimum resistor value is 4k with set resistors.
As you rolled up the resistance to max pot value
10k + 4k is 14k
14k with 10n is approx 1100 Hz
So it could be a adjustable filter from 1100 to 4000 Hz
And since you only need .5 Q
both capacitors and resistors will be equal.
Making the circuit a bundle of fun since both resistors are equal.
It is incredibly easy to make it a adjustable filter.
Which you could also predict with Virtuix Cad.
Using a common Dual Gang 10k potentiometer
Minimum resistor value is 4k with set resistors.
As you rolled up the resistance to max pot value
10k + 4k is 14k
14k with 10n is approx 1100 Hz
So it could be a adjustable filter from 1100 to 4000 Hz
Of course this is a simplified circuit.
Showing the Filter RC networks
output is shown AC coupled and needed.
real world circuit could probably use a input buffer, not shown
and power supply rails need to be decoupled with 10u and 10n to 100n capacitors
also not shown again for simplicity
likely layout puts 10u Caps some distance from opamp because of size.
but for stability 10n to 100n decoupling caps are placed directly on supply pins
or as close as possible to supply pins
Showing the Filter RC networks
output is shown AC coupled and needed.
real world circuit could probably use a input buffer, not shown
and power supply rails need to be decoupled with 10u and 10n to 100n capacitors
also not shown again for simplicity
likely layout puts 10u Caps some distance from opamp because of size.
but for stability 10n to 100n decoupling caps are placed directly on supply pins
or as close as possible to supply pins
Something more complete with input buffer.
Power supply decoupling etc etc.
Shown with very common general purpose audio Dual Opamp TL072
of course use what is desired, the filter and buffer are unity gain
So the op amp must be unity gain stable.
Normally C3,C8 are mounted as close as possibly to the opamp pins
For stability. as mentioned in post #26
Keep in mind 100n is more common value for General purpose
opamps from 1 to 15 MHz bandwidth
Usually much faster opamps from 50 MHz to 100 MHz would use smaller
10n as shown.
I wrote 1k to 4k adjustable
realize now it should have noted 1k to 4k is the filter cutoff.
hopefully not causing confusion for resistance value.
R4, R5 set minimum resistance value 4k for 4k filter cutoff
P1 at full rotation 10k + 4k for 14k
14k will yield 1.1k filter cutoff as shown in graph in post #26
Power supply decoupling etc etc.
Shown with very common general purpose audio Dual Opamp TL072
of course use what is desired, the filter and buffer are unity gain
So the op amp must be unity gain stable.
Normally C3,C8 are mounted as close as possibly to the opamp pins
For stability. as mentioned in post #26
Keep in mind 100n is more common value for General purpose
opamps from 1 to 15 MHz bandwidth
Usually much faster opamps from 50 MHz to 100 MHz would use smaller
10n as shown.
I wrote 1k to 4k adjustable
realize now it should have noted 1k to 4k is the filter cutoff.
hopefully not causing confusion for resistance value.
R4, R5 set minimum resistance value 4k for 4k filter cutoff
P1 at full rotation 10k + 4k for 14k
14k will yield 1.1k filter cutoff as shown in graph in post #26
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and if I want to make a bandpass filter or low-pass filter should I also design with those cap values?
When it comes to audio opamp circuits, I would start with TI's application notes / reference circuits. If you don't find appropriate ones in the datasheet or product page, look for the "Eval or demo" boards and get the schematic from them.
This is an expensive way to do it as TI will promote their latest and greatest ICs.
I went this approach for a PC2704 USB DAC output LPF I was doing PCB for. What I ended up having to order was 2 TI OPA opamps costing about £8 each. But it gave me the circuit pre-analysed and I believe even a TI filter design application link for it.
This PCB in fact: (don't look closely if you have OCD, some of the resistors are up-side down!)
This is an expensive way to do it as TI will promote their latest and greatest ICs.
I went this approach for a PC2704 USB DAC output LPF I was doing PCB for. What I ended up having to order was 2 TI OPA opamps costing about £8 each. But it gave me the circuit pre-analysed and I believe even a TI filter design application link for it.
This PCB in fact: (don't look closely if you have OCD, some of the resistors are up-side down!)
Really depends on the cutoff frequency you desire.
I just tend to use the smallest cap value possible
since they fit on the board easier and lower cost of course.
also as mentioned for low noise I like to keep resistor values
around 8 to 12k.
So again depending on desired cutoff frequency, I tend to play with
the cap value so the resistors dont exceed 8 to 12k ideally.
of course eventually depending how low the frequency is.
you will be forced to use larger capacitors. no way around it.
and the resulting resistor values as well can be higher than 12k.
also if trying to make a adjustable filter using common 10k or 100k dual gang or quad gang potentiometers
the resulting capacitor value will have to be necessary to achieve the desired cutoff.
Yes indeed, most of which are revised copies of National Semiconductors work.
and of course Fairchild before National bought them.
all in the past now of course. But National Semi had some darn good spice simulation guides
making filter design extremely less painful. Impossible to cross reference since Texas dudes rebranded everything.
Then again later on Texas Instruments did some darn good filter calculators
where spice wasnt needed. And likely the better calculators I have seen.
Included what is now available online in a more cloud type of app.
As in before you could actually download a filter app and not have to be online.
Anyways almost any circuit you might need with a opamp is
National Semiconductors AN-31 Op amp Circuit Collection
far as the Texas Boys
Thomas R Brown should credited with
Handbook of Operational Amplifier Applications.
you know back in the 60's when a op amp symbol
kinda looked funny...LOL
Anyways, Bruce Carter updated a lot of Thomas Browns
early work. And eventually caught on and became very popular
and later published as a book
Hence the ever so popular
Op amps for Everyone
All 3 of these publications easily found in PDF for free on the net
And if anybody is starting or familiar with opamps
almost anything you need to know.
Aside from single supply operation.
And again National Semiconductor has many Application Notes for
Single Supply. All of course rebranded as TI material now
On TI and "how things change". I was recently reviewing a device datasheet and trying to learn about it's SPI slave select behaviour and timing. The trouble is, the latest revision of the datasheet is marked as "Introducing inclusive language". So the words Master and Slave have been removed. Replaced with "Device" and "Controller", which not only doesn't describe the relationship, but also... it's next to impossible to search for "Device" OR "Controller" in a datasheet and not get 95% false positives. I suppose I should find the previous revisions before woke history rewrite took place.
In NXP it's now leader and follower... Completely insane, but at least you probably wouldn't get the false positives with those terms.
Did MISO and MOSI also change into CIDO and CODI?
Did MISO and MOSI also change into CIDO and CODI?
So called "inclusive language" has NOTHING to do in Technical/Physics/Science/Engineering language.
"Device" is so generic it means NOTHING specific, certainly it does not describe ANY Function.
It is TI who MUST NOT introduce Politically charged language in a Technical Datasheet.
"Device" is so generic it means NOTHING specific, certainly it does not describe ANY Function.
It is TI who MUST NOT introduce Politically charged language in a Technical Datasheet.