Q on Transistor

[Wong]

Hi,

Is it possible to saturate the NPN BJT transistor in this biasing ?
Vcc
___
|
|
|
_| C
B |
---- Resistor ----|
|
-
| E
|---------------- Output
|
Resistor
|
|
|
---
- Ground


Since the transistor is OFF when '0' to base and hence output is '0'.
Then when '1' to base I would like to have 4.5V at the output, is that
possible to bias the transistor in saturation region (since Vce no
more <0.2V)?

 

[John Popelish]

Rich Grise wrote:

On Fri, 15 Oct 2004 02:12:31 -0700, Wong wrote:

Hi,

Is it possible to saturate the NPN BJT transistor in this biasing ?
Vcc
___
|
|
|
_| C
B |
---- Resistor ----|
|
-
| E
|---------------- Output
|
Resistor
|
|
|
---
- Ground


Since the transistor is OFF when '0' to base and hence output is '0'.
Then when '1' to base I would like to have 4.5V at the output, is that
possible to bias the transistor in saturation region (since Vce no
more <0.2V)?

Is "saturation" even meaningful in an emitter follower?

Sure. Saturation implies that the collector to emitter voltage is
less than the base to emitter voltage (the collector to base junction
becomes forward biased). If this circuit is driven with a voltage
more positive than the collector supply, the transistor may well
saturate.

--
John Popelish

 

[Wong]

tatto0_2000@yahoo.com (Wong) wrote in message news:<509bfe22.0410150112.7c079369@posting.google.com>...

Hi,

Is it possible to saturate the NPN BJT transistor in this biasing ?
Vcc
___
|
|
|
_| C
B |
---- Resistor ----|
|
-
| E
|---------------- Output
|
Resistor
|
|
|
---
- Ground


Since the transistor is OFF when '0' to base and hence output is '0'.
Then when '1' to base I would like to have 4.5V at the output, is that
possible to bias the transistor in saturation region (since Vce no
more <0.2V)?

OK, one more question.
If my transistor datasheet stated that the minimum hFE (DC current
transfer ratio) is 100 and the maximum is 400, can I still force this
transistor into saturation where hFE normally is 10 in saturated
transistor?

Thank you.