multi bjt analysis- anlysis circuits with more than one bjt or any transistor

[h.galeh]

there are many bjt circuits around
i caught up many of them . but they unfortunately hava 2 or more bjts
how we can understand their working area . -> aalysis?
a circuit:
it controls automobiles battery . cutting below 10 volts . but how it works?
**broken link removed**
thank you

 

[Miguel Gaspar]

First you must start with one BJT (or mosfet) circuits to develop skills and know what a circuit do when you see it.
there are two mayor strategies in desig: modular and two port analisys
a) Modular design is whe you develop your design as a block that will be no afected whe you conect to it another one.
b) develop the analisys considering that when you conect another circuit it will modify the operation of both circuits.

Without a circuit it is very difficult to say how it works.