Hello,there is an intresting structure shown bellow, i can that there is a form of switch being used.
from mosfet i know that Vgate above Vt opens the transistor.
But here the bjt's are in weird forms .
how can i interpret the logic of this circuit?
Thanks.

 

When "in" is connected to GND, both out1 and out2 are enabled.

ak

 

Why Q1 has a resistor connected between base and collector

 

To assure that Q1 turns off if the IN input signal is an open circuit (floating).

ak

 

A door opens or closes.
A transistor turns on or turns off.

The schematic looks confusing because Vdd_3 and the emitter of the PNP transistor should be near the top of the schematic.

 

Hello AnalogKid,for a switch we need to use saturation region as shown bellow.
How to simulate this phenomena of floating point input BJT in ltspice?
Thanks

 

the bjt's are in weird forms .

They look like normal LT Spice transistors to me. What do mean by "weird forms"?

ak

 

"The bjt's are in weird forms"?
I looked in Google for Transistor Symbols and most transistors had a circle around them but a few did not.
A copy of a simulation was the only symbol with the arrow without being completely filled in:

 

When "in" is connected to GND, both out1 and out2 are enabled.

ak

Only out2 is enabled.

 

Hello,first I have picked an PNP transistor as shown bellow,It has the following caracteristics of Vbe sweeps.
then i tried to simulate the first part of the circuit shown bellow.
I know that this is a floating point protection connection but what to connect to the collector in order to simulate the floating input?
I also dont know what what is a floating point voltage.
Thanks.

 

Your PNP transistor is in a circuit with positive voltages but a PNP uses only negative voltages, or a positive emitter.
Your base will burn out with it grounded and a positive voltage on the collector because nothing limits the current.
The collector will burn out with 360mA in it.
A simulation usually wrongly allows severe overloading.

 

In my previos reply i showed work and simulation and I asked about the floating point protection mechanism

 

In my previos reply i showed work and simulation and I asked about the floating point protection mechanism

Google and I have never heard about it.
The polarities and currents in your PNP transistor circuit are completely wrong.

 

Hello Audioguru,i am trying to undestand what Analog kid suggested.

To assure that Q1 turns off if the IN input signal is an open circuit (floating).

ak

 

Hello Audioguru,i am trying to undestand what Analog kid suggested.

Yef, you wrongly asked, " Why Q1 has a resistor connected between base and collector" but it is not connected to the collector, instead it connects between base and emitter to make sure that the transistor is turned off when the base is floating.

 

Floating point?

 

Hello ,i am used to work with mosfets.
in mosfet we have Vgs>Vt to open or close and Vdg>Vt to see the formula of the biased current going threw the transistor.
I tried to read the following tutorial but i dont have this innecquality conditions in PNP .
What the the voltage innequality conditions so i could see exactly if its open or closed and what current goes threw the PNP ?
Thanks.

https://www.electronics-tutorials.ws/transistor/tran_4.html

 

Your PNP transistor circuit is completely wrong.
Here are corrections:

 

Hello Audio guru, i am looking for explanation that shows PNP as if its a mosfet.
I want to know what voltage /current innequality should i use so i will know that PNP is OPEN.
and in what state ,(in mosfet its linear or saturation) so i know the exact formula of the current that goes threw.

 

Has it occurred to you that a PNP is not a MOSFET, and hence no such inequalities exist?