Help me design a PSU

[nemail2]

sure, there are several caps for stabilization in the circuit. two on the opamps for voltage and current control, an input- and an output-cap.

i have built the psu already, nothing oscillates so far. did test it with resistive, capacitive and inductive loads.

[VEGETA]

sure, there are several caps for stabilization in the circuit. two on the opamps for voltage and current control, an input- and an output-cap.

i have built the psu already, nothing oscillates so far. did test it with resistive, capacitive and inductive loads.

How much max voltage and current does it output?

Can it work with pre-regulator? down to 1v diff for example?

[nemail2]

How much max voltage and current does it output?

Can it work with pre-regulator? down to 1v diff for example?

Dave did implement a pre-regulator, however he never finished the µSupply (until now, he says from time to time that it IS actually happening).

My design does not have a pre-regulator but I might implement that later, maybe.

The PSU does 0-12V (potentially 0-20V but you'll have to change the Opamp supply line and pay attention to the linear regulators power dissipation as well as maybe tune some other parts to the higher voltage) and 0-4A. if you change the opamp gain, you'll get out even more amps, however you'd also have to pay attention to heat dissipation, especially without the pre-regulator and at low output voltages.

[Efe_114]

To make it go down to 0v you would need a negative rail. To make this very easy for you, get ICL7660 charge pump IC. Feed it with say 5v and it will output -5v with low current of course.

This will be the negative rail of your op-amp which sets the output voltage... it could be something like +25v positive rail and -5v negative rail which will ensure 0v output.

It is better to put more filtering caps on 7660 output since it generates lots of noise, or better yes as I did in my dummy load design.. which is to give 9v to 7660 so it outputs -9v (or -8v with losses) then put TL431 after it which generates 2.5v in my case (you can make it anything via 2 resistors) with very low noise, now add another 100uF cap after it and you'll be done.

I hope this helps you.

when i was re-reading the replies i re-noticed this comment and i came up with these questions:
why do i need negative rail? if im going to use darlington pair and op-amp. i could use a lm358 which could go down to 0 volts with single supply? i didnt understand why do i need to use op amp. dont i need negative supply for lm317 adj pin ? I am confused. which configuration i can use 7660 lm358 tl431 and lm317 in the same time?(as you say in the next reply)

[nemail2]

when i was re-reading the replies i re-noticed this comment and i came up with these questions:
why do i need negative rail? if im going to use darlington pair and op-amp. i could use a lm358 which could go down to 0 volts with single supply? i didnt understand why do i need to use op amp. dont i need negative supply for lm317 adj pin ? I am confused. which configuration i can use 7660 lm358 tl431 and lm317 in the same time?(as you say in the next reply)

if you are going to use a darlington and an opamp like LM358 oder OPA2197 (like I do in my design), you won't need a negative rail. if using a DAC to set the voltage, you'd be basically limited by the minimum voltage the DAC can output + opamp gain you'll be using (e.g. DAC can output 5mV * opamp gain of 3, would give you 15mV minimum output voltage). of course if your opamp can't output such a low voltage, you'll be limited by the opamp. but basically you can go pretty low without having a negative rail here (I do that, and it works perfectly).

if you are going to use an LM317 you'll need a negative supply if you want to go all the way down to zero to negate the minimum output voltage of about 1,2V of the LM317. but I wouldn't do that, might make the LM317 under certain circumstances.

you do need an opamp for the darlington because in this constellation the opamp would be the "controlling device" which in the end sets and maintains the voltage you wanna have. you can apply current to the base of a darlington but how'd you know the voltage it will allow to pass?
with an opamp, you feed in the voltage you want into the non inverting terminal of the opamp, the opamp output goes to the darlington base and the darlington emitter goes to the inverting terminal of the opamp. the opamp will output whatever voltage it has to (limited by its supply voltage) to make the inverting and non-inverting inputs the same. so it will do whatever it can so the output voltage of the darlington matches the input voltage at it's non-inverting terminal.
because you don't have DACs which can output tens of volts usually, you'll want to put a gain into the opamp circuit to increase the maximum output voltage (e.g. DAC output is 5V max, you want 20V so you have to put in a gain of 4). also, I think only opamps which are "unity gain stable" can be used without any gain resistors. the datasheet will tell you if your opamp is unity-gain stable. for other opamps, you'll need a gain to make them work stable.
there is much more into making opamp circuits stable than I understand so here would some real PRO have to kick in but I hope you get an idea of what it is all about.

[AngraMelo]

Efe,

I know it can be a pain to source components when you dont have a digikey/mouser type of vendor in your country, believe me, Im in Brazil and here sucks as well.

Now, for the more experienced guys to help you (and I do not include myself in the middle of them). You do need to specify somethings.
If you want something around 15V, your 48V transformer probably wont do (or at least wont do with a simple design).

Usually, the hard things to get for us are ICs and other specialized things. So you probably have access to general use diodes, resistors and transistors.
So with that in mind we need to get another thing straight. You are trying to learn with the project as well as achieve your goals, now, do you know a little bit about transistors and opamps? If you dont building a PS using an opamp to control de voltage and cascading transistors to get the current you need might be the right solution for you. If you dont have access to an opamp using a simple zener that will set up the max Voltage limit and using a pot to vary that voltage (and still using the cascading transistors) might give you what you want.
It seems that you can follow and build circuits from a ready made schematic and what you are looking for is learning more about how the things work and starting to customize the circuits for what you need. Unfortunately asking for help here will not give you that. When you ask for help to build a simple PS you will get a ready made schematic and thus not learning what you are actually wanting to lear which is design the circuit yourself.
The guys here are incredibly helpful and knowledgable but you kind need to ask the right question.

My suggestion is: If you know how to build LM317`s (and other simple voltage regulator ICs) circuits, if you have a good idea how to use transistors and opamps then you need to add more features to your PS to make the project more challenging. If you dont know how to use transistors and opamps I strongly encourage you to built a couple of simple PS`s using them, even if it doesnt have a proper V regulation, and then starting asking questions about how to tweak the circuit to get the current limiting, proper regulation, less noise...

[Efe_114]

Efe,

I know it can be a pain to source components when you dont have a digikey/mouser type of vendor in your country, believe me, Im in Brazil and here sucks as well.

Now, for the more experienced guys to help you (and I do not include myself in the middle of them). You do need to specify somethings.
If you want something around 15V, your 48V transformer probably wont do (or at least wont do with a simple design).

Usually, the hard things to get for us are ICs and other specialized things. So you probably have access to general use diodes, resistors and transistors.
So with that in mind we need to get another thing straight. You are trying to learn with the project as well as achieve your goals, now, do you know a little bit about transistors and opamps? If you dont building a PS using an opamp to control de voltage and cascading transistors to get the current you need might be the right solution for you. If you dont have access to an opamp using a simple zener that will set up the max Voltage limit and using a pot to vary that voltage (and still using the cascading transistors) might give you what you want.
It seems that you can follow and build circuits from a ready made schematic and what you are looking for is learning more about how the things work and starting to customize the circuits for what you need. Unfortunately asking for help here will not give you that. When you ask for help to build a simple PS you will get a ready made schematic and thus not learning what you are actually wanting to lear which is design the circuit yourself.
The guys here are incredibly helpful and knowledgable but you kind need to ask the right question.

My suggestion is: If you know how to build LM317`s (and other simple voltage regulator ICs) circuits, if you have a good idea how to use transistors and opamps then you need to add more features to your PS to make the project more challenging. If you dont know how to use transistors and opamps I strongly encourage you to built a couple of simple PS`s using them, even if it doesnt have a proper V regulation, and then starting asking questions about how to tweak the circuit to get the current limiting, proper regulation, less noise...

yes, i think due to my poor english i couldnt express myself right. the title shouldnt be "help...." everyone was so helpful and helped me a lot even tough i couldnt pick the title correctly . i know op-amps transistors, ADCs, DACs, MOSFETs,capacitors inductors and more but i am not even close to being proffesional i dont have such experience. yes i cant find special ICs but i can find jellybean op-amps transistors, but everything i can find are fake, generally they are tend to not work i have to buy 5 to get 2 working , I think for the final design i will buy all the components from farnell and wait 30-40 days shipping and pay extreme shipping and probably a whopping-120%-tax (i tried to buy 100 euro hakko 888d and i had to pay 250 euro in total ) i think i will go with 2n3055 darlington pair,  a fast op-amp, some stabilizing caps , a CC sink circuitry for constant load.

[AngraMelo]

Efe,

I know it can be a pain to source components when you dont have a digikey/mouser type of vendor in your country, believe me, Im in Brazil and here sucks as well.

Now, for the more experienced guys to help you (and I do not include myself in the middle of them). You do need to specify somethings.
If you want something around 15V, your 48V transformer probably wont do (or at least wont do with a simple design).

Usually, the hard things to get for us are ICs and other specialized things. So you probably have access to general use diodes, resistors and transistors.
So with that in mind we need to get another thing straight. You are trying to learn with the project as well as achieve your goals, now, do you know a little bit about transistors and opamps? If you dont building a PS using an opamp to control de voltage and cascading transistors to get the current you need might be the right solution for you. If you dont have access to an opamp using a simple zener that will set up the max Voltage limit and using a pot to vary that voltage (and still using the cascading transistors) might give you what you want.
It seems that you can follow and build circuits from a ready made schematic and what you are looking for is learning more about how the things work and starting to customize the circuits for what you need. Unfortunately asking for help here will not give you that. When you ask for help to build a simple PS you will get a ready made schematic and thus not learning what you are actually wanting to lear which is design the circuit yourself.
The guys here are incredibly helpful and knowledgable but you kind need to ask the right question.

My suggestion is: If you know how to build LM317`s (and other simple voltage regulator ICs) circuits, if you have a good idea how to use transistors and opamps then you need to add more features to your PS to make the project more challenging. If you dont know how to use transistors and opamps I strongly encourage you to built a couple of simple PS`s using them, even if it doesnt have a proper V regulation, and then starting asking questions about how to tweak the circuit to get the current limiting, proper regulation, less noise...

yes, i think due to my poor english i couldnt express myself right. the title shouldnt be "help...." everyone was so helpful and helped me a lot even tough i couldnt pick the title correctly . i know op-amps transistors, ADCs, DACs, MOSFETs,capacitors inductors and more but i am not even close to being proffesional i dont have such experience. yes i cant find special ICs but i can find jellybean op-amps transistors, but everything i can find are fake, generally they are tend to not work i have to buy 5 to get 2 working , I think for the final design i will buy all the components from farnell and wait 30-40 days shipping and pay extreme shipping and probably a whopping-120%-tax (i tried to buy 100 euro hakko 888d and i had to pay 250 euro in total ) i think i will go with 2n3055 darlington pair,  a fast op-amp, some stabilizing caps , a CC sink circuitry for constant load.

Awesome! So you have a pretty good idea of what you are doing!! Im sure you will find plenty of help here! Good luck, buddy!!
Im in the exact same situation as you, building a couple PSs and having to deal with huge taxes and a lack of good components.
If you dont mind me asking, where are you from?

[rstofer]

No matter what marketing says, rail-to-rail op amps can't go to 0V and still source or sink current.  They just can't.  Think about the active device that would be pulling down toward the 0V rail.  It has to have SOME voltage drop.

So, instead of having 0V as the lower op amp supply, we use -1V or so.

The problem is the spec and that is the death of most of these projects.  A) It's very hard to get to 0V.  Change the spec to "approach 0V" and accept 1V or 1.5V minimum.  B) Relatively high voltage and current spec (particularly current) when there is no possible use for such high values.  Somebody sees it written somewhere and suddenly 30V 5A becomes a thing.  Sure, the commercial guys can do it but they can get transformers wound any way they want and they can design in switching relays.  You just shouldn't drop 60V at 3A across the  pass transistor but the math is what it is!  Whatever the input capacitor voltage is, minus whatever the output voltage is, times the current, is turned to heat in the pass transistor.  Note that the heat goes up as the output voltage goes down!

In the days of CMOS, 100 mA is pretty high current.  1A is completely over the top.  Now, it's true, I'm not building audio amplifiers for a parade ground but those would have dedicated supplies anyway.  Around the digital bench, 1A is a LOT.  We also don't need variable voltage, 3.3V, 5V, +-15V covers just about everything.

Yes, when you are learning about analog circuits, an adjustable supply is nice.  But it doesn't need to go above 15V or above 1A.  I might build such a thing with an LM317 and call it a day.  BTW, I would pay a lot of attention to Figure 3 of this datasheet.

https://www.st.com/resource/en/datasheet/lm217.pdf

Don't overlook 5V 2A wall warts.  I use them all the time!

[spec]

The ultimate barrier to getting true zero volts from a PSU without a negative rail, is leakage current. The output transistors leak current quite a bit and the killer is that the leakage current increases exponentially with junction temperature- take a look at the data sheet for your output devices.

Quite often with many PSUs, you are dissipating a lot of power in the output transistors, so the junction temperature is high and leakage current becomes a real problem.

But, bearing in mind that a PSU is a power amplifier, there is another aspect. If you have no way of loosing the leakage current, or you have no current drain on the output stage, you get into a no-mans land where the changing characteristics of the output transistors can cause problems.

The solution is quite simple though:
[1] Either generate a negative supply (2 x caps, 2 x diodes)
[2] Or use a power diode and a constant current sink, of around 20mA (power diode, 1 x small signal transistors, 1 x medium power transistor, 2 x resistors)

In general, a minimum constant current drain is good news as it also provides some current sinking in addition to current sourcing, which is handy for some loads.

Of course, the ultimate is a current sink capability equal to or more than the maximum source output current capability of the PSU (similar output stage to an audio or servo power amplifier). The LT1118 three terminal regulator, does this.

https://www.analog.com/media/en/technical-documentation/data-sheets/1118fd.pdf

[nemail2]

i'm not entirely sure what you guys are talking about. i'm going down to 15 mV output voltage without any negative rail, as mentioned earlier.

[BravoV]

Alternative design , -> General Purpose Power Supply Design

Quoting the designer ...

"... I am only looking a very low cost high performance regulator that could be controlled by just plain potentiometers."


Read the 1st post carefully.


A sneak peek on the spec (highlighted few items that might interest you) :

3V to 30V input source voltage range
1.5V dropout voltage
True regulation down to zero volts
1A output current with 0 to 1A current limit
High level of protection from loads.
Transient performance similar to the LT3080
No-load to full load output voltage regulation  better then 0.001% (Wiring and track resistance is the biggest problem)
Loads like a battery can be connected to the supply while the supply is off without causing any problems to the supply or the battery.
Design based on "garden' components - potential to make it very cheap.
Possibility of a wide range 1A supply using only board mounted devices and no heatsink.

Oh yes, no negative rail needed. 

A sneak peek ...



Again, you need to read the whole thread, just a suggestion.

[Efe_114]

No matter what marketing says, rail-to-rail op amps can't go to 0V and still source or sink current.  They just can't.  Think about the active device that would be pulling down toward the 0V rail.  It has to have SOME voltage drop.

So, instead of having 0V as the lower op amp supply, we use -1V or so.

The problem is the spec and that is the death of most of these projects.  A) It's very hard to get to 0V.  Change the spec to "approach 0V" and accept 1V or 1.5V minimum.  B) Relatively high voltage and current spec (particularly current) when there is no possible use for such high values.  Somebody sees it written somewhere and suddenly 30V 5A becomes a thing.  Sure, the commercial guys can do it but they can get transformers wound any way they want and they can design in switching relays.  You just shouldn't drop 60V at 3A across the  pass transistor but the math is what it is!  Whatever the input capacitor voltage is, minus whatever the output voltage is, times the current, is turned to heat in the pass transistor.  Note that the heat goes up as the output voltage goes down!

In the days of CMOS, 100 mA is pretty high current.  1A is completely over the top.  Now, it's true, I'm not building audio amplifiers for a parade ground but those would have dedicated supplies anyway.  Around the digital bench, 1A is a LOT.  We also don't need variable voltage, 3.3V, 5V, +-15V covers just about everything.

Yes, when you are learning about analog circuits, an adjustable supply is nice.  But it doesn't need to go above 15V or above 1A.  I might build such a thing with an LM317 and call it a day.  BTW, I would pay a lot of attention to Figure 3 of this datasheet.

https://www.st.com/resource/en/datasheet/lm217.pdf

Don't overlook 5V 2A wall warts.  I use them all the time!

Dont get me wrong but i think you misunderstood something i am already planning for 15v 1A. i know 1A is a lot but i will use a power transistor so why not go up to 1A( i wasnt planning more than that anytime) i bought a 48 v transformer but that was for the kit someone posted a picture of.I will buy a lower voltage transformer specifically for this project which i think will be 24 volts or maybe 18 volts but 18 volt ones are pretty rare i will buy a toroidal one if possible. thank you for the suggestion so i will use ICL7660 charge pump IC to generate negative rail (-5 Volts) Also is it needed to make it with 15v/10v taps? I am deciding to use a 2n3055 so i think 15W max wouldnt be a problem for TO3 package. As i said i dont have much experience at all so i am planning all of these in theory So anyone here have more reccomendations to me about problems that will appear on practice?

[Efe_114]

The ultimate barrier to getting true zero volts from a PSU without a negative rail, is leakage current. The output transistors leak current quite a bit and the killer is that the leakage current increases exponentially with junction temperature- take a look at the data sheet for your output devices.

Quite often with many PSUs, you are dissipating a lot of power in the output transistors, so the junction temperature is high and leakage current becomes a real problem.

But, bearing in mind that a PSU is a power amplifier, there is another aspect. If you have no way of loosing the leakage current, or you have no current drain on the output stage, you get into a no-mans land where the changing characteristics of the output transistors can cause problems.

The solution is quite simple though:
[1] Either generate a negative supply (2 x caps, 2 x diodes)
[2] Or use a power diode and a constant current sink, of around 20mA (power diode, 1 x small signal transistors, 1 x medium power transistor, 2 x resistors)

In general, a minimum constant current drain is good news as it also provides some current sinking in addition to current sourcing, which is handy for some loads.

Of course, the ultimate is a current sink capability equal to or more than the maximum source output current capability of the PSU (similar output stage to an audio or servo power amplifier). The LT1118 three terminal regulator, does this.

https://www.analog.com/media/en/technical-documentation/data-sheets/1118fd.pdf

yes im planning a 20 mA CC sink circuitry to serve as a minimum load.

[Efe_114]

Alternative design , -> General Purpose Power Supply Design

Quoting the designer ...

"... I am only looking a very low cost high performance regulator that could be controlled by just plain potentiometers."


Read the 1st post carefully.


A sneak peek on the spec (highlighted few items that might interest you) :

3V to 30V input source voltage range
1.5V dropout voltage
True regulation down to zero volts
1A output current with 0 to 1A current limit
High level of protection from loads.
Transient performance similar to the LT3080
No-load to full load output voltage regulation  better then 0.001% (Wiring and track resistance is the biggest problem)
Loads like a battery can be connected to the supply while the supply is off without causing any problems to the supply or the battery.
Design based on "garden' components - potential to make it very cheap.
Possibility of a wide range 1A supply using only board mounted devices and no heatsink.

Oh yes, no negative rail needed. 

A sneak peek ...



Again, you need to read the whole thread, just a suggestion.

wow thanks thats really intresting i will read it. that specs are very nice. especcially the RED ones!

[AngraMelo]

Alternative design , -> General Purpose Power Supply Design

Quoting the designer ...

"... I am only looking a very low cost high performance regulator that could be controlled by just plain potentiometers."


Read the 1st post carefully.


A sneak peek on the spec (highlighted few items that might interest you) :

3V to 30V input source voltage range
1.5V dropout voltage
True regulation down to zero volts
1A output current with 0 to 1A current limit
High level of protection from loads.
Transient performance similar to the LT3080
No-load to full load output voltage regulation  better then 0.001% (Wiring and track resistance is the biggest problem)
Loads like a battery can be connected to the supply while the supply is off without causing any problems to the supply or the battery.
Design based on "garden' components - potential to make it very cheap.
Possibility of a wide range 1A supply using only board mounted devices and no heatsink.

Oh yes, no negative rail needed. 

A sneak peek ...



Again, you need to read the whole thread, just a suggestion.

Bravo, what is use of the RC circuits shunting the OPamps output and input? (beginner here)

[nemail2]

i have a 18V AC outputting transformator and i'm doing 4A current with a pair of TIP3055/BD139 Darlingtons from 0-12V without an issue. proper heatsink and fan req'd, of course.
at 1V output voltage and below it gets quite hot obviously but it has temperature monitoring and emergency shutoff just in case and besides, what hobbyist needs currents like this at such low voltages, anyway. 3.3V or even 2.5V at 4A it does without any issue.

[Kleinstein]

Alternative design , -> General Purpose Power Supply Design

Quoting the designer ...

"... I am only looking a very low cost high performance regulator that could be controlled by just plain potentiometers."


Read the 1st post carefully.


A sneak peek on the spec (highlighted few items that might interest you) :

3V to 30V input source voltage range
1.5V dropout voltage
True regulation down to zero volts
1A output current with 0 to 1A current limit
High level of protection from loads.
Transient performance similar to the LT3080
No-load to full load output voltage regulation  better then 0.001% (Wiring and track resistance is the biggest problem)
Loads like a battery can be connected to the supply while the supply is off without causing any problems to the supply or the battery.
Design based on "garden' components - potential to make it very cheap.
Possibility of a wide range 1A supply using only board mounted devices and no heatsink.

Oh yes, no negative rail needed. 

A sneak peek ...



Again, you need to read the whole thread, just a suggestion.

Bravo, what is use of the RC circuits shunting the OPamps output and input? (beginner here)

The RC elements at the OPs are there to set the frequency response of the regulators. So they decide wether the supply works well, is too slow or oscillates because it tries to be too fast. Getting this part right is the real difficulty.

Trying to get 1 A with no heat sink would usually requite a switched mode supply, or a lot of transistors like 2N3055 that might work with no heat sink up to maybe 2 w. In a linear power supply there is quite some possible heat produced and not much to change with this.

It gets tricky to go down all the way to zero without a negative supply, as the typical BJT based constant current sink only works down to some 10-50 mV if one tries hard. So a negative auxiliary supply, even if only - 100 mV already helps a lot. This could be as little as 2 extra diodes with less voltage drop and a filter cap.

[Efe_114]

I just recieved my order and i started experimenting with TIP142 and i found out voltage jumps up when i it hook up to a load. about 0.3 volts for a 1w power Led. and the worst thing is that overshoot doesnt recover! what could be the reason of it? Im using lm358 as a opamp TIP142 as series pass transistor a pot for referance a 100nF ceramic cap between opamp output and -input.

[fsr]

I think that analyzing that will require a schematic. I don't get the part about the capacitor feedback. Only a capacitor would mean no DC feedback at all. And a pot for reference? Took from where? Please, show us a schematic.

[Efe_114]

schematic at attachment. I couldnt figure out how can i convert kicad to pdf and didnt see the attachment button down there and  converted it to jpg and tried with add image function and it didnt work and i finally figured out attachment button. first time sending something as attachment. so it took quite a while

[fsr]

Well, you can capture the screen and save it to a PNG file, probably easier than exporting to PDF.

Why is that capacitor there? It doesn't seems like it can do much as it's connected. The voltage at the (-) input will be 2 Vbe below the opamp's output, no matter what.

Your circuit will buffer whatever voltage you have on the potentiometer's wiper, but if Vcc has noise, or ripple, or goes up or down, so is your output voltage. So, your output can only be regulated if Vcc is well regulated already.

At this point, you may want to take a look at how national made it with the LM317. I attached and image with the functional schematic. That's how they did a variable voltage regulator.
To get how the LM317 works, just remember that an opamp with negative feedback will try to set it's output voltage to a value that causes it's two inputs to match.

[Kleinstein]

schematic at attachment. I couldnt figure out how can i convert kicad to pdf and didnt see the attachment button down there and  converted it to jpg and tried with add image function and it didnt work and i finally figured out attachment button. first time sending something as attachment. so it took quite a while

The minimal circuit would need at least an extra resistor in the connection between the output and the OPs inverting input.

[Efe_114]

Well, you can capture the screen and save it to a PNG file, probably easier than exporting to PDF.

Why is that capacitor there? It doesn't seems like it can do much as it's connected. The voltage at the (-) input will be 2 Vbe below the opamp's output, no matter what.

Your circuit will buffer whatever voltage you have on the potentiometer's wiper, but if Vcc has noise, or ripple, or goes up or down, so is your output voltage. So, your output can only be regulated if Vcc is well regulated already.

At this point, you may want to take a look at how national made it with the LM317. I attached and image with the functional schematic. That's how they did a variable voltage regulator.
To get how the LM317 works, just remember that an opamp with negative feedback will try to set it's output voltage to a value that causes it's two inputs to match.

but im not measuring referance voltage im measuring output voltage and i power a load output voltage rises up i dont mean the ripple, the ouput voltage rises.

schematic at attachment. I couldnt figure out how can i convert kicad to pdf and didnt see the attachment button down there and  converted it to jpg and tried with add image function and it didnt work and i finally figured out attachment button. first time sending something as attachment. so it took quite a while

The minimal circuit would need at least an extra resistor in the connection between the output and the OPs inverting input.

i didnt know a resistor is needed. it says only a capacitor in art of electronics. not speccifically "ONLY" but it says a capacitor

[Efe_114]

Whatever i tried i wasnt able to fix it  . Any help?