multiple bjt switch circuit interpretation

Thread Starter

yef smith

Joined Aug 2, 2020
239
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.

1620678581349.png
 

Thread Starter

yef smith

Joined Aug 2, 2020
239
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
1620762312652.png
 

Audioguru again

Joined Oct 21, 2019
3,174
"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:
 

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Thread Starter

yef smith

Joined Aug 2, 2020
239
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.

1620844643645.png

1620845523976.png
 

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Last edited:

Audioguru again

Joined Oct 21, 2019
3,174
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.
 

Thread Starter

yef smith

Joined Aug 2, 2020
239
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
1620935203014.png
 

Thread Starter

yef smith

Joined Aug 2, 2020
239
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.
 
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