Hi,
This clip from the circuit is to show the plot of the resistance of the IRFZ over the PWL voltage range of 4.0V through 4.2V.
The resistance of the IRFZ varies from 140R down to 10R, for a vg of 4.0V through 4.2V.
It is not coupled to the original circuit, it is for demonstration only.

Your pulse 0V to 5V will not work.
E

 

Hi,
This clip from the circuit is to show the plot of the resistance of the IRFZ over the PWL voltage range of 4.0V through 4.2V.
The resistance of the IRFZ varies from 140R down to 10R, for a vg of 4.0V through 4.2V.
It is not coupled to the original circuit, it is for demonstration only.

Your pulse 0V to 5V will not work.
E

View attachment 327534

I used an opamp to multiply the voltage so I can have like 4 to 8. My purpose was to set the smoothened pulse into opamp and forward the output to nmos gate like the first version. When we set for example 2v from a supply it works but from a capacitor it did not work.
What I mean is when we used same built but not the capacitor, it worked.

 

Hi , I was looking about active filters and luckly found what kind of filter you shared with me to study really early.
I made a design , used a online calculator for the component values but the mid frequency was 35khz in the simulation instead of 40khz so I changed values without checking the correcting formulas and now it acts not as it supposed to at all.
Here is the ac analysis and the transistient output. I have not tried It over breadboard yet. I also need to note that , I can track the echo pulse over osilloscope screen from 30cms with previous circuit that we discuss about yesterday. But with a better filter I guess I can have better output and I can learn a lot.Can you tell me about the key points? Is it the right approach to design and adjust based on estimation?
EDIT : I've also made an narrowband filter and I added it too.

 

Hi demi,
In the 'friendly' circuit you have U2 as a AD822 and the other a NE5322.
This image shows the change in the frequency plot when using NE5532.
Note: I changed the resistor values to suit the NR5532
E

 

Hi , I was looking about active filters and luckly found what kind of filter you shared with me to study really early.
I made a design , used a online calculator for the component values but the mid frequency was 35khz in the simulation instead of 40khz so I changed values without checking the correcting formulas and now it acts not as it supposed to at all.
Here is the ac analysis and the transistient output. I have not tried It over breadboard yet. I also need to note that , I can track the echo pulse over osilloscope screen from 30cms with previous circuit that we discuss about yesterday. But with a better filter I guess I can have better output and I can learn a lot.
EDIT : I've also made an narrowband filter and I added it too.
Since I do not have much experience with this kind of circuits , can you tell me about the key points? Is it the right approach to design and adjust based on estimation?

View attachment 327598
View attachment 327599
View attachment 327601

Hi demi,
In the 'friendly' circuit you have U2 as a AD822 and the other a NE5322.
This image shows the change in the frequency plot when using NE5532.
Note: I changed the resistor values to suit the NR5532
E
View attachment 327628

Hi Eric, I used ne5532 as simply amplifier and the first opamp as Active filter.

 

Hi demi,
In the 'friendly' circuit you have U2 as a AD822 and the other a NE5322.
This image shows the change in the frequency plot when using NE5532.
Note: I changed the resistor values to suit the NR5532
E
View attachment 327628

They both ne5532 and I mentioned sonething else too pls review.

 

Hi demi,
Have you compared the specifications in the datasheets of the two OPA's AD822 and NE5532.?

You can see on those response plots the different OPAs give a different frequency peak.
E

 

Hi demi,
Have you compared the specifications in the datasheets of the two OPA's AD822 and NE5532.?

You can see on those response plots the different OPAs give a different frequency peak.
E

I do sir, I Will not use ne5532 for this filter. In first example you uplladed 2 pole filter but I made a one pole one. In the circuit I upload I used Ad822 as filter and ne5532 as amplifier.
In practical, Ad822 is expensive for me and I checked if I can use Lf353 and seems like it can be used

 

Hi demi,
The LF353 is also a dual voltage powered OPA.
Draw up the friendly circuit using the LF353 and we can compare the performance, do an AC analysis simulation, post the result.
E

 

Hi demi,
The LF353 is also a dual voltage powered OPA.
Draw up the friendly circuit using the LF353 and we can compare the performance, do an AC analysis simulation, post the result.
E

I could not find a Spice model for lf353 sir. Anyways I will recheck. Is the thing I've tried is correct ? Considering I used AD822 and Ne5532 can you tell about the points that could be better. Since I am learning I wonder if my design is okey or has minor-major mistakes.

 

Hi demi,
The LF353 is also a dual voltage powered OPA.
Draw up the friendly circuit using the LF353 and we can compare the performance, do an AC analysis simulation, post the result.
E

Hi Eric, here is the friendly filter using LF353
Mid frequency is 42Khz
EDIT: I've uploaded narrow filter which seems working so well I guess.

 

Hi demi,
That looks acceptable, what is the next step in your project?
E
Can you also change the plot background to White from Black makes it easier to read on a PC screen.

BTW:
Bu eser için en az bir porsiyon Tabak Tatlısı'nı bekleyeceğim.

 

Hi demi,
That looks acceptable, what is the next step in your project?
E
Can you also change the plot background to White from Black makes it easier to read on a PC screen.

BTW:
Bu eser için en az bir porsiyon Tabak Tatlısı'nı bekleyeceğim.

View attachment 327639

Hi Eric , It is literally does not matter for me where u are from but when you write some spesific text in Turkish it makes me laugh.
My next step , I will test this built onboard and analysis how far I can track the echo signal and if I can track it so I can rearrange the gain in case of it is needed.
I am planning to use zener diode and opamp built that I shared at #95.
Since I do not have swept gain , I do need to arrange the gain and the Vref matching. As I see , a better working filter - repectively to older builts - is espectially needed over here.

 

Hi Eric, I've tried the circuit and I all got is 16khz huge gained noise...
Here is oscilloscope output. Blue traces is straight from piezo , yellow traces is the LF353's non inverting inpu - through a capacitor to block dc to help me view -.

This is the cirucit I tested with bright background

 

Hi Eric, I've tried the circuit and I all got is 16khz huge gained noise...
Here is oscilloscope output. Blue traces is straight from piezo , yellow traces is the LF353's non inverting inpu - through a capacitor to block dc to help me view -.
View attachment 327678
This is the cirucit I tested with bright background
View attachment 327679

This is the oscillating part.

 

Hi demi,
I have tried a number of tests on that circuit section, I cannot make it go unstable and oscillate.

The problem maybe your circuit layout and decoupling.
E
This image is a single pulse input response at 12.5uS/50uS

 

Hi demi,
I have tried a number of tests on that circuit section, I cannot make it go unstable and oscillate.

The problem maybe your circuit layout and decoupling.
E
This image is a single pulse input response at 12.5uS/50uS

View attachment 327702

Hi Eric , I learned about this oscillating might be caused of multiplefeedback mechanism but I could not find any solution.
Do you have any suggestions ?

 

Hi demi,
Look through this PDF and link.
One of the main causes is capacitive loads on the OPA outputs.

E

https://www.analog.com/en/resources...-to-avoid-instability-capacitive-loading.html

 

Hi demi,
Look through this PDF and link.
One of the main causes is capacitive loads on the OPA outputs.

E

https://www.analog.com/en/resources...-to-avoid-instability-capacitive-loading.html

But when nothing connected at output it oscillates anyways. I tried few ways In the link but could not get anything. The old worse filter was at least working haha. At this point I feel confused. May should I use old built with decreasing ref voltage at comparator and use that ?

 

HI demi,
That is puzzling.
Try using your other OPA types and check for oscillation.
Post a photo of the layout, In know it's a PITA, but I may be able to see a problem.
E