Hi!. I've got a question. Why the base resistor changes in related to the C-E resistance in order to achive the saturation stage?. I mean, the transistor doesn,t have a fix value to achieve this stage?. Why this happens?.

 

What is the "base resistor"?

 

What is the "base resistor"?

Yes, i mean the resistor that you use in the base of the transistor.

 

Yes, i mean the resistor that you use in the base of the transistor.

"in the base" ? Either you mean (a) the differential resistance rbe BETWEEN the base node and the emitter node or (b) an EXTERNAL resistor between a voltage source and the input at the base.

 

Or are you asking, in the case of a grounded emitter transistor inverter, why base drive current needs to increase in order to keep the transistor saturated when the collector load decreases?

 

Circuit schematic is the language of electronics.
Post a circuit schematic.

 

Hi!. I've got a question. Why the base resistor changes in related to the C-E resistance in order to achive the saturation stage?. I mean, the transistor doesn,t have a fix value to achieve this stage?. Why this happens?.

This is in Homework Help. Post the complete text of the problem and any associated schematic.

 

The TS is from Spain, this is the text of post #7

El mensaje en la publicación #7 es importante.
"Esto está en Ayuda con la tarea. Publique el texto completo del problema y cualquier esquema asociado".

 

the transistor doesn,t have a fix value to achieve this stage?

No.
A BJT transistor is considered technically to be a voltage operated device but the collector-emitter current is also proportional to the base-emitter current once a base-emitter voltage of about 0.6V is reached.
Look at the current-gain value (beta or hfe) value in the transistors data sheet.

For good saturation, a base current of 1/10 the collector current is usually recommended.

As to why, that just the way a bjt works.