Why do we -usually- have to use a DC voltage (power supply) to bias the transistor?

 

Why do we -usually- have to use a DC voltage (power supply) to bias the transistor?

Because the difference is bias point is what we're more interested in. If bias point was unstable, results would be invalid.

 

Why do we -usually- have to use a DC voltage (power supply) to bias the transistor?

It's more fun that way.

 

You can't use AC to bias a transistor, so DC is all that's left.

 

Usually you say? You are wasting everybody's time.

 

Why do we -usually- have to use a DC voltage (power supply) to bias the transistor?

(100 words or less ...)

The objective of setting a bias point in a transistor circuit is to put the transistor into conduction but not saturation. An input AC signal increases or decreases the conduction to produce a full waveform out.

Setting this bias point determines the class of the amplifier. What input voltage will produce what kind of output.

 

You can't use AC to bias a transistor

how about Ge ones? or the attachment? -ss

 

Imagine I have a 4-metre high wall to paint.

I can only reach the lower 2 metres while standing on the ground.
Hence I have to bias my height upwards by standing on a 2-metre step ladder.
Now I can paint from the centre of the wall and cover the whole height.

Hope this helps.

 

Because a transistor is a one way DC device. It's a pilot check valve. We can keep the check valve open a little bit (if we want to) with DC bias.

 

If you look at the specs.for a transistor it starts at zero and goes into saturation.
Normally biasing is used to allow it to operate in a linear manner for regular use.
However you can bias it to operate anywhere along the graph.Since it is a non linear device
square,log,cube and all sorts of outputs can be achieved.Therefore you bias it to get an output
that is suited for the project being design.

 

how about Ge ones? or the attachment? -ss

Why do you think they would be different?
Re: attachments
Enough base current to turn them on.

 

Imagine I have a 4-metre high wall to paint.

I can only reach the lower 2 metres while standing on the ground.
Hence I have to bias my height upwards by standing on a 2-metre step ladder.
Now I can paint from the centre of the wall and cover the whole height.

Hope this helps.

Good, and in 100 words or less.

 

Re: attachments

as amazing as it may sound i don't think - i watch and stay baffled about what the spice is showing

however the tunnel diodes have negative impedance - those things are quantum mechanics devices - i won't go predicting what is or is not possible here - if you tell me how to measure the circuits without signifficantly affecting (pushing) their operation - id likely made it clear

 

as amazing as it may sound i don't think - i watch and stay baffled about what the spice is showing

however the tunnel diodes have negative impedance - those things are quantum mechanics devices - i won't go predicting what is or is not possible here - if you tell me how to measure the circuits without signifficantly affecting (pushing) their operation - id likely made it clear

Isn't everything a quantum mechanics device?