Open collector opamp like LM393?

Hi,

there's no LM393 component, is there? If not, how can I simulate it, or any open collector opamp?
By simulate I mean design the circuit with the pull-up restor connected to the output. Do you see what I mean?

Thanks.

Hi.
You can add an open collector buffer at the output of an opamp.

arcachofo wrote:Hi.
You can add an open collector buffer at the output of an opamp.

Hi,

a few questions:

1. by 'open collector buffer' you mean a special component (in that case where is it?) or a buffer type with open drain? (In that case where should I put the pull-up resistor? after it?)
   
2. what voltage should I check in in the opamp? 0 V?
   

1- Yes, a buffer with open drain.
And resistor at the output of the buffer.

2- I don't understand what you mean.

In any case all depends on what you are doing, another solution could be a diode or transistor at the output of the opamp.

arcachofo wrote:1- Yes, a buffer with open drain.
And resistor at the output of the buffer.

2- I don't understand what you mean.

In any case all depends on what you are doing, another solution could be a diode or transistor at the output of the opamp.

Sorry, In number 2 I meant to say 'what voltage should I type in'. Anyway, forget about it, as the solution iis number 1.

What I'm trying to do is reproduce a circuit with an LM393, As it is an open collector opamp, I want to place the pull-up resistor and see how it behaves. Am I making myself understood?

I've tried adding the resistor, as you suggested, after the buffer, but it won't work.

I've tried adding the resistor, as you suggested, after the buffer, but it won't work.

Can you share your circuit?

In order to help a bit in this post, I am including a subcircuit for the LM339 (open collector) and several examples to use. you have to study them a bit and also the subcircuit in the data folder of the zip.

LM339 (4 OPAMS), LM393 (2 OPAMPS).

I hope they are useful to you.

Good luck.

Defran wrote:In order to help a bit in this post, I am including a subcircuit for the LM339 (open collector) and several examples to use. you have to study them a bit and also the subcircuit in the data folder of the zip.

LM339 (4 OPAMS), LM393 (2 OPAMPS).

I hope they are useful to you.

Good luck.

Hi Defran. Lots of thanks!!! I think this is what I was looking for. LM393 is not included, but don't worry. It'll be an excuse to create it myself following your package. If I have any questions I'll come back to you.

Thanks again.

Well, here you have the same but with the LM393...

Defran wrote:Well, here you have the same but with the LM393...

Hi Defran. Thanks for the 393. I was working on it. I was modifying your 339.

I have a few questios (excuse my ignorance):

1. One of your examples, the one I'm sending you is the case I was looking for. You use a 100 ohms resistor, but that's not a pull-up resistor, is it? In your case the LED gets on when the Vin+ > Vin-, but if I put a 4K7 resistor it doesn't, or at least it does but very dimmly.
   
2. In the creation  of the component you use a buffer. Why?
   
3. I've tried to register both components in my SimulIDE but when I drag and drop them I get a plain opamp but not the boards: 8 and 4 pins respectively. I get an opamp symbol inside a square.
   
4. I thought the package and the circuit names should be the same.
   

blitobyte wrote:

Defran wrote:Well, here you have the same but with the LM393...

Hi Defran. Thanks for the 393. I was working on it. I was modifying your 339.

I have a few questios (excuse my ignorance):

1. One of your examples, the one I'm sending you is the case I was looking for. You use a 100 ohms resistor, but that's not a pull-up resistor, is it? In your case the LED gets on when the Vin+ > Vin-, but if I put a 4K7 resistor it doesn't, or at least it does but very dimmly.
   
2. In the creation  of the component you use a buffer. Why?
   
3. I've tried to register both components in my SimulIDE but when I drag and drop them I get a plain opamp but not the boards: 8 and 4 pins respectively. I get an opamp symbol inside a square.
   
4. I thought the package and the circuit names should be the same.
   

Sorry I forgot the circuit

1.- The 100 ohms resistor in the output of the LM393 to 5v is a typical pullup, yes. Its function is to polarize the output transistor collector. In the case of your example the vaue of 100 ohms is to work the LED when the output transistor of the LM393 is in OFF. When this is in ON, the voltage in collector will be 0.8v maximum and the LED does not work, because the LEDS need 1.5v typically. Other higher pullup values will make the LED look less.

2.- In my LM393 subcircuit I add a buffer to convert the output of the Standard Primitive Opamp of Simulide in Open Collector (this means that the LM393 can only be used as comparator). See it in the buffer Properties.

3.- The file 0_INVIS.png in the data folder of my LM393 subcircuit is to make invisible its background.

4.- Yes it is needed, but the package file should typically be informative of its Pinout, NEVER for operational use. In the particular case of the multicircuits and obtaining its individualized use over the LS package (Logical Symbol) it is espetially necessary that the package file does not exist or that it has another extension. This is essential to avoid collisions between the two.

Defran wrote:1.- The 100 ohms resistor in the output of the LM393 to 5v is a typical pullup, yes. Its function is to polarize the output transistor collector. In the case of your example the vaue of 100 ohms is to work the LED when the output transistor of the LM393 is in OFF. When this is in ON, the voltage in collector will be 0.8v maximum and the LED does not work, because the LEDS need 1.5v typically. Other higher pullup values will make the LED look less.

2.- In my LM393 subcircuit I add a buffer to convert the output of the Standard Primitive Opamp of Simulide in Open Collector (this means that the LM393 can only be used as comparator). See it in the buffer Properties.

3.- The file 0_INVIS.png in the data folder of my LM393 subcircuit is to make invisible its background.

4.- Yes it is needed, but the package file should typically be informative of its Pinout, NEVER for operational use. In the particular case of the multicircuits and obtaining its individualized use over the LS package (Logical Symbol) it is espetially necessary that the package file does not exist or that it has another extension. This is essential to avoid collisions between the two.

Thanks Defran... too much for me. First things first:

1. I think I've already mentioned I am a hobbist studying electronics. My knowledge is quite limited... so far. I understood pull-up/down resistors were used to attach a floating pin to a specific value, either positive or negative. I also thought they should be high to let voltage pass but not current (???), therefore their 'high value' in the range of K's.100 ohms i not high, is it?
   
2. About the image mask I don't really understand it. Never mind. I'll come to it when I understand the rest.
   
3. I've made a component' for the LM393 but it won't work. Could yo please have a look at it and tell me why it is not working? 'm sending it to you.
   
   
   
   
   

1.- The value of the discrete components must be the one necessary for their function in a scheme.

2.- Simulide is the best tool to practice electronics, but the creation of subcircuits is not the best way to learn how to use it or to practice electronics. You should leave this part for when you know more.

3.- Due a bug in Simulide you cannot put the sign "-" in "Pin Id", replace it with a letter for example "m", and also in its corresponding tunnel.

Defran wrote:1.- The value of the discrete components must be the one necessary for their function in a scheme.

2.- Simulide is the best tool to practice electronics, but the creation of subcircuits is not the best way to learn how to use it or to practice electronics. You should leave this part for when you know more.

3.- Due a bug in Simulide you cannot put the sign "-" in "Pin Id", replace it with a letter for example "m", and also in its corresponding tunnel.

Changed + and -. Now it works.

Thanks

Hello,
Bouncing on this opamp/comp topic : I was trying to replicate the LM339 comparator block diagram with Simulide ; however I am "stumbling" on the different constant current sources and was wondering how it could be elegantly done with simulide ?



All insights much appreciated :-) !

Hello,
Bouncing on this opamp/comp topic : I was trying to replicate the LM339 comparator block diagram with Simulide ; however I am "stumbling" on the different constant current sources and was wondering how it could be elegantly done with simulide ?

Hi, there is a current source in the development branch:
https://simulide.forumotion.com/t550-simulide-trunk-tester-builds#2961

Ok I'll have a look at that - thanks for your support !

Update :
I guess it is working as expected in the attached diagram; however, when used as controlled current, should not the arrow be reversed ?
Also small bug with the voltage source I think ; the voltage value displayed does not always follow the actual voltage.

(using R1751/win64 here :-)