about transistor biasing method

[Bhuvanesh Nick]

see the above image .in first circuit i added 0.1 ohm resistance i got around 6 v in emmiter side.and then i replaced it with 2.1k then i got 11v as out put .this is why and my supply is 12 v

plzz help me

 

[chuckey]

With an emitter load of the DVM (10M ohms), what you are measuring is thermal leakage current, the answer should be ~0V with any reasonable load.
Frank

 

[FvM]

Did you intend to forward bias the collector-base junction as shown in the schematic? You would destroy the transistor in the first circuit.

 

[goldsmith]

about transistor biasing method

screenshot-17-.png

see the above image .in first circuit i added 0.1 ohm resistance i got around 6 v in emmiter side.and then i replaced it with 2.1k then i got 11v as out put .this is why and my supply is 12 v

plzz help me

Hi Bhuvanesh Nick
As "FvM" mentioned above you are destroying your transistor in first circuit . when a transistor is about to be biased in active region CB junction must be at reverse bias . and BE in forward bias . and of course the current of that must be limited via a suitable resistor in avoid that our transistor being destructed .
When you want your BJT being saturated concept says the CB junction must be in forward bias but it doesn't mean that we make it a forward bias . it would be in forward bias by behavior of your circuit automatically . the reason that BE should be in forward bias in active region ( instead of CB ) is that BE can go through the zener region and deliver avalanche breaking after 5 volt ( approx ) and we don't want that .

Best Wishes
Goldsmith

 

[Bhuvanesh Nick]

With an emitter load of the DVM (10M ohms), what you are measuring is thermal leakage current, the answer should be ~0V with any reasonable load.
Frank

dvm means and what it meant 10m ohms.

 

[Venkadesh_M]

dvm means and what it meant 10m ohms.

DVM is digital volt meter, and a volt meter should be connected parallel to a load,
and you didnt put any load on the circuit and apparently it was 10M ohm...

 

[Bhuvanesh Nick]

Hi Bhuvanesh Nick
As "FvM" mentioned above you are destroying your transistor in first circuit . when a transistor is about to be biased in active region CB junction must be at reverse bias . and BE in forward bias . and of course the current of that must be limited via a suitable resistor in avoid that our transistor being destructed .
When you want your BJT being saturated concept says the CB junction must be in forward bias but it doesn't mean that we make it a forward bias . it would be in forward bias by behavior of your circuit automatically . the reason that BE should be in forward bias in active region ( instead of CB ) is that BE can go through the zener region and deliver avalanche breaking after 5 volt ( approx ) and we don't want that .

Best Wishes
Goldsmith

what this sentence means..plz some more detial explaination and what is fvm?

When you want your BJT being saturated concept says the CB junction must be in forward bias but it doesn't mean that we make it a forward bias . it would be in forward bias by behavior of your circuit automatically

 

[FvM]

When you want your BJT being saturated concept says the CB junction must be in forward bias but it doesn't mean that we make it a forward bias . it would be in forward bias by behavior of your circuit automatically

You misunderstood the point. It's simply about a reversed battery in your simulation circuit. You would connect the collector of a PNP to the negative battery terminal but you connected it to the positive, which explains your strange simaulation results.

 

[goldsmith]

what this sentence means..plz some more detial explaination and what is fvm?

Ha ha ! What is ? you'd better to say who is . everybody know him here as well . he is the guy which his post is above my post . he is one of the most expert engineers that you can see during your life .

When you want your BJT being saturated concept says the CB junction must be in forward bias but it doesn't mean that we make it a forward bias . it would be in forward bias by behavior of your circuit automatically

"FvM" has explained the point as well in his post : #8 .


Good Luck
Goldsmith

 

[Bhuvanesh Nick]

Ha ha ! What is ? you'd better to say who is . everybody know him here as well . he is the guy which his post is above my post . he is one of the most expert engineers that you can see during your life .


"FvM" has explained the point as well in his post : #8 .


Good Luck
Goldsmith

sorry about that.my intention is is to make it as swith. for that if i use resistors on collector and base is the works good.

- - - Updated - - -

Did you intend to forward bias the collector-base junction as shown in the schematic? You would destroy the transistor in the first circuit.

.my intention is is to make it as swith. for that if i use resistors on collector and base is the works good

 

[Venkadesh_M]

my intention is is to make it as swith. for that if i use resistors on collector and base is the works good

Are you got your problem solved ?

 

[FvM]

if i use resistors on collector and base is the works good

Maybe in a different circuit (with correct battery polarity)?

 

[goldsmith]

.my intention is is to make it as swith. for that if i use resistors on collector and base is the works good

What kind of switch ? just on/off ? with what frequency ? how much is the required current through the switch ?