was Re:Ir-remote Now is: Op Amp discussion

[MP1]

... then much of my proof gets deleted.
I am the one who has been backstabbed, since you and the rest of our community did not join-in.
Isn't this an adult forum for discussions?

audioguru, when you add offensive or insulting comments in your posts I will delete them. I am not going to waste my time editing your posts. As an adult, you should be able to handle this concept.

But I have seen that you understand this already, since you always re-post with the offensive comments left out. This tells me that you already know why it was deleted.

MP

 

[audioguru2]

When op amps are powered from dual (bi-polar) supplies, the center tap of the supplies are connected to ground. Any input sources connected to ground are automatically referenced to the center of the supply voltage, so the output voltage is automatically referenced to ground. .... thus biasing must be employed to ensure that the output voltage swings between the correct voltages.

Therefore, the circuit which is using the bi-polar supply does not need the bias voltage.

Wired,
Thanks for joining this discussion, but your statements are confusing:
In your 1st paragraph above, you agree with me and my posted tutorial that opamp inputs must not be floating and must be referenced to ground.
But in your 2nd paragraph above, you allow a floating input.

Are you going to add a bias resistor to ground on the floating input of the opamp in the IR project's receiver, or not?
Don't you agree that when the opamp's input is referenced to ground by the added resistor, instead of floating, then the project will have an improved sensitivity?

 

[wired1]

You have misquoted my post. There is no confusion in my comments. I spoke of two different methods of connection. Single supply and Bipolar supply. They have different requirements. Op-amps operated on a Single Supply need a bias resistor. Op-amps operated on a Bipolar Supply do not require a bias resistor because both inputs on the op-amp with bipolar supply are referenced to the center of the total supply, which is zero volts.
Op-Amps are a subject unto themselves. You would benefit from taking a course on them at your local university.

 

[audioguru2]

Op-amps operated on a Bipolar Supply do not require a bias resistor because both inputs on the op-amp with bipolar supply are referenced to the center of the total supply, which is zero volts.

Wired,
I am sorry that you disagree with me and my nearby university, from which I recently posted their opamp tutorial.
In your quote above, you say that "BOTH inputs on the opamp with bipolar supply are referenced to....... zero volts". I agree, that is correct.
Perhaps you have not seen the circuit that we are talking about.
Where is the zero volts reference on the floating input pin #3 of this opamp?View attachment 35450

 

[MP1]

Wired, welcome to the community. Please feel free to ignore audioguru. We had a similar conversation about Darlingtons. Sorry that you are getting so much opposition from your first two posts. I hope it does not give you a bad taste.

MP

 

[audioguru2]

Show me a floating input on a buffer/follower opamp or any other opamp circuit.
Try it. Make a 741 circuit with a small (10nF) input capacitor but no bias resistor, and watch its output sink to near the negative supply, and stay there, just like our project.
No, an opamp CANNOT have a floating input to work properly.

MP and/or Wired,
Why ignore me? You might learn something important.

You didn't comment on my University Opamp Tutorial, which explained that BOTH inputs should have a voltage reference.
My University is well respected, and so is National Semiconductor.
In the latter's Application Note #20, An Applications Guide For Opamps, page 2 describes "The Non-inverting Amplifier" (which is what we are discussing):
"The amplifier output will go into saturation if the input is allowed to float".

That is exactly what I say in my quote, above, and have been saying all along.
The Application Note is here:
http://www.national.com/an/AN/AN-20.pdf

The opamp cannot work properly without having a voltage reference (ground, in our application) on its non-inverting input.
And darlingtons work fine with base-emitter resistors that I recommended, that you said would make them "not work properly".

 

[wired1]

audioguru: I have not read your posted tutorial and therefore I do not know whether I agree with it or not. I do not intend to continue to go head to head with you or anyone else regarding simple op-amp theory. In my original post, I pointed out that you do not need a bias voltage from the power supply added to an op-amp that is run from a bipolar supply. The inputs are referenced to ground, which is the center point of a bipolar supply. Perhaps you disagree with this. So be it. Move on.
In the circuit that you have posted, I know nothing about it, do not have a parts list, nor do I know what the second IC is, but it appears to be an AC or pulsed active circuit. In which case, the pin with the capacitor connected to it is not floating when the field is collapsing and there is capacitive reactance. Perhaps this is what this circuit is meant to do since there is a DC blocking capacitor at the output of the op-amp. Again, I do not intend to spend time in debate with you.
If your purpose here is trying to determine if this circuit works, I must point out that you have spent days in debate when you could breadboard this circuit in minutes to make such a determination.
In reference to your comment, "Why ignore me? You might learn something important". I do not think anyone with your attitude would be able to teach me anything. I now fully understand the prior comments posted by ante.

 

[audioguru2]

MP, or your new name, Wired,
You're welcome.
I'm glad to help members get their theory straight.

 

[ante1]

audioguru,

I tried not to interfere but now I could not resist any longer, tell me is your next step to chase ghosts ?

Ante :

 

[audioguru2]

Ante,
Welcome back.

No ghosts, just faulty circuits and incorrect statements.

 

[MP1]

yes, audioguru, everyone who disagrees with you is me in disguise. Of the 2330 members now on this forum, I hold 2326 of the user names...
You will have to guess who the other three true identities are :

MP

 

[audioguru2]

Well, at least The Guelph University, and National Semiconductor agree with me.
Do you think that they will become members?

 

[wired1]

I thought this was a place where I would find good discussion in electronics. Seems I was wrong.

 

[Kevin Weddle]

It seems simple enough to me. The input can be grounded or grounded through a resistor. There is the case where you want the input bias currents to be the same, for a zero voltage output. This is the resistor which will allow you to affect the input bias current. I think the resistor is for opamps that don't have a null offset pot.

 

[audioguru2]

Wired,
There are many good discussions about electronics at this place.
Please join-in if you have good proof for your arguments, as I have.

Kevin,
The missing resistor provides a VOLTAGE reference of 0V to the non-inverting input of the opamp, not a current source, since the opamp's input current is very, very small.
Offset current equaling or its adjustment is not neccessary for this circuit.

 

[MP1]

Wired,
There are many good discussions about electronics at this place.
Please join-in if you have good proof for your arguments, as I have.

audioguru, since when does this forum give you the right to tell people when they can join a discussion? No one has to prove anything in this forum to discuss electronics. >

The bottom line is this: I think you just trampled on a new member and sent him away pissed off simply because he did not agree with your views. Then told him he could join in the discussion if he has proof.
This is not allowable.

...as far as I am concerned: you are wrong and, no, I am not going to waste my time to find you the proof. It is an application I use in real life ....and I will join any discussion I please, even with lack of the proof you require.
(as you can see, when you drive people away from the forum, it pisses me off)

MP

 

[audioguru2]

35 posts because of only one missing resistor?

 

[MP1]

...which is not missing in the first place.

MP

 

[audioguru2]

You didn't comment on my University Opamp Tutorial, which explained that BOTH inputs should have a voltage reference.
My University is well respected, and so is National Semiconductor.
In the latter's Application Note #20, An Applications Guide For Opamps, page 2 describes "The Non-inverting Amplifier" (which is what we are discussing):
"The amplifier output will go into saturation if the input is allowed to float".

That is exactly what I say in my quote, above, and have been saying all along.
The Application Note is here:
http://www.national.com/an/AN/AN-20.pdf

The opamp cannot work properly without having a voltage reference (ground, in our application) on its non-inverting input.
You still don't believe my University nor National Semiconductor?

 

[audioguru2]

Here's another one who believes that an input resistor is important in an opamp circuit:
http://sound.westhost.com/dwopa.htm