http://www.learningaboutelectronics.com/Articles/Voltage-divider-bias-of-a-BJT-transistor

In this site, internal resistance of base is R1 || R2.

what does '||' mean?

and why is 10K ohms the standard?

 

http://www.learningaboutelectronics.com/Articles/Voltage-divider-bias-of-a-BJT-transistor

In this site, internal resistance of base is R1 || R2.

R1 || R2 is the base circuit resistance, the resistance the base "sees" looking out. For example, it would determine the change in base voltage for a given change in base current.

what does '||' mean?

It means "in parallel with", so "R1 || R2" means "R1 in parallel with R2".

and why is 10K ohms the standard?

I did not see 10k being referred to as a standard.

 

R1 || R2 is the base circuit resistance, the resistance the base "sees" looking out. For example, it would determine the change in base voltage for a given change in base current.



It means "in parallel with", so "R1 || R2" means "R1 in parallel with R2".



I did not see 10k being referred to as a standard.

then why Rb = R1 || R2 ?? could you let me know about it ??
are R1 and R2 not connected in series?

 

If we assume that and ideal power supply has an impedance of 0 Ohms with respect to ground then both of the ends of the divider are connected to 0 Ohms with respect to ground and as far as impedance (or resistance) is concerned the two are in parallel.

 

If we assume that and ideal power supply has an impedance of 0 Ohms with respect to ground then both of the ends of the divider are connected to 0 Ohms with respect to ground and as far as impedance (or resistance) is concerned the two are in parallel.

I can't understand.. ㅜㅜ

 

If you take an ideal battery and draw some current from it, ideally the voltage will not change.We say that an ideal battery has an internal resistance of zero ohms, and that is because if you put current into or take current out of an ideal battery the voltage will not change.

If you take 100 microamps into or out of the divider in the circuit below you will see the voltage at the output of the divider change by 100 uA x 16k = 1.6 volts. (perform the experiment and see). An ideal power supply has the same 0 Ohm internal resistance as the battery.

 

See

 

If you take an ideal battery and draw some current from it, ideally the voltage will not change.We say that an ideal battery has an internal resistance of zero ohms, and that is because if you put current into or take current out of an ideal battery the voltage will not change.

If you take 100 microamps into or out of the divider in the circuit below you will see the voltage at the output of the divider change by 100 uA x 16k = 1.6 volts. (perform the experiment and see). An ideal power supply has the same 0 Ohm internal resistance as the battery.

View attachment 133447

Thank you for your kind teaching.

 

See
View attachment 133448

Thank you very much!