I was reviewing/following a tutorial describing the pros/cons of various transistor base biasing configurations. Configuration #4 is shown above. Resistor Rb2 was added to what was previously Configuration #3. The circuit with the text is shown below (in quotes)....
Why does adding Rb2 increase stability with respect to variations in Beta, ( β ) by increasing the current flowing through the base biasing resistors? The unclear (to me) original text is below. Thanks
"Adding an additional resistor to the base bias network of the previous configuration improves stability even more with respect to variations in Beta, ( β ) by increasing the current flowing through the base biasing resistors.
The current flowing through RB1 is generally set at a value equal to about 10% of collector current, IC. Obviously it must also be greater than the base current required for the minimum value of Beta, β.
One of the advantages of this type of self biasing configuration is that the resistors provide both automatic biasing and Rf feedback at the same time."