I don't know how to figure out the current in each transistor base and current of the art of electronics chapter 2. "The “divider” formed by R2R3 may be confusing: R3s job is to keep Q3 off when Q1 is off; and when Q1 pulls its collector low, most of its collector current comes from R3’s base (because only ~0.6mA of the 4.4 mA collector current comes from R3 - make sure you understand why)."

 

When Q2 is on, what will be the base-emitter voltage of Q3?

 

Pls help me read the art of electronics book chapter 2, you'll see d the circuit diagram. Thanks

 

Please answer my quiestion. I can clearly see both the circuit digram in your post, and your question.

 

The Vbe of a biased transistor looks like this -

As you can see when it is forward biased the Vbe is close to a constant.

Regards, Dana.

 

Please try and read chapter 2 of the book particularly page 76 and 77 of the art of electronics where transistor is used as a switch.

 

Have you see this ?
https://electronics.stackexchange.c...s-voltage-dividers-or-should-they-be-analyzed

 

Jony130 thank you. All others who wishes to help but due to inadequate details thanks too