Difference between floating base and grounded base of transistor

[electronic_satya]

Hi All,

Could someone please let me know if there is any differnce between a floating base and a grounded base in a common emitter configuration transistor? If in a circuit if i find the transistor base floating can i assume that Base current is "0". Is this valid in multistage amplifier as well?

Thanks in advance,
Regards

 

[Syncopator]

In a common emitter stage, the emitter is connected, either directly or through a resistor, to what is usually called "ground". The input is between base and emitter, output between collector and emitter.

A "grounded" base is normally called common base. Input between emitter and base, output between collector and base.

I can't say that I've heard of "floating base" before.

 

[electronic_satya]

I was just referring to the following circuit the parameters given are alpha1 = 0.98, alpha2 = 0.96 Vcc=24V Rc = 120ohm Ie = -100mA. I need to find all the currents and voltages. So can I asume that Ib1 =0 under all conditions? Could someone guide me to understand this question?

Thanks in advance,
regards,

 

[LvW]

..So can I asume that Ib1 =0 under all conditions? Could someone guide me to understand this question?

No, just the opposite!
You should know that it is quite normal that some circuit diagrams do NOT show voltage or current sources. Instead, only some symbols are shown at the corresponding nodes indicating that for normal operation a voltage or a current is to be applied. In your case, a current Ib1 flows into the base - and it does not matter from where it comes. Assume any source you like.