Balun? Basic question

[LNA]

I'm confused with this 2 types of balun. What's the difference? Can I use them for IF path to convert single-ended to balunced?

Thanks.

 

[E Kafeman]

Main difference is 90 degree ;-).
The one at left seems to have a core and one connection more.
A balun got its name from BALanced UNbalanced, so that is the main function for all baluns.
Core and type of winding gives a balun different properties such as impedance ratio, power handling, internal loss and frequency range, so that is what you need to check to find out if it fulfill your needs.

 

[LNA]

That's what I guessed. It's easier for me to understand the right one.

My confusion is, If pin 1 of the left one is single-ended input, the output at pin4 and pin6 would be in phase and same amplitude would not be a differential output. Is it correct? then in what kind of application this balun would be used?

 

[E Kafeman]

As long as main load is between 4&6 it will be differential output. This is the normal operation for any balun.
Not all baluns have an center-tapped winding (pin 5). Main use of it is to connect to ground for better signal balance under some circumstances.

 

[LNA]

Main difference is 90 degree ;-).
The one at left seems to have a core and one connection more.
.

Did you mean difference between input and output? not the difference between the output 2 pins?

Main use of it is to connect to ground for better signal balance under some circumstances.

Can you elabrate this? maybe examples? appreciated.

 

[E Kafeman]

Both these baluns in your picture are winded exactly the same way, have same connections, and can do the same job in a circuit, if its other data such as frequency range fits.
In your picture is one balun rotated 90 degree compared to the other but else do they electrically do the same thing.
One of them do also have a schematic symbol for a core. It is not unusual that an RF balun is designed without core so both things occur IRL.

 

[LNA]

I misunderstood your first reply on the 90 degree. Now I got it.

What about the dots? The right one has a dot at input side and a dot at output which I think means the output would be in phase with input.

However the left one had 4 dots at output. what do they mean?

 

[E Kafeman]

Dots on the left one is not directly related to output pins, it is a common way to show winding direction.
Coil at right, those dots are not any standard markings. My guess is that it is markings that also can be found at the actual coil as an orientation.
Check data sheet for this coil where it probably is explained.
Baluns causes always some phase delay between input and output. If balanced side really is balanced should it not matter how you connect it.