Laptop Power Supplies

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Bias

Bias

You all are talking about bias voltage adding to the load of a computer.

Isn't bias voltage a parameter of analog circuitry? That is one of the main advantages of using digital it doesn't hold a higher voltage to a lower voltage so it can swing either way.

I know there are still places that a bias voltage has to be applied like maybe the processor oscillator but they are fewer than before.

Ronald
 
Hi Ronald,

My choice of words above, especially "bias", is almost certainly not technically accurate. I apologize for the confusion it might be creating.

"Bias voltage", as I recall, comes from tube technology which largely was centered on voltage amplifiers.

Transistors are current amplifiers, by and large. If I were coaxing a transistor to produce an analog output, say a sine wave of an amplitude that wasn't clipped by the limits of the transistor, I'd put a bias current on the base that would put a mid-range current on the collector, then I'd vary the base current in the pattern of a sine wave, producing a corresponding current pattern on the transistor collector.

With digital signals, the 1 and 0 or, rather, the ON and OFF, current is either flowing or not. With each individual transistor, there isn't a bias current per se. When taken as a group on a chip of hundreds of thousands or millions of transistors, however, when the chip is powered and configured as a logic component of the overall computer, a significant percentage of the transistors will be ON, will be conducting, all the time, just not the same transistors, all the time. All the transistors that are conducting, holding a bit of information in steady state, until needed are the cause of what I called "bias current" in my post above.
 
Hello Al

Been a long time since my electronics days.Talking about the bias voltage. I read something some where the other day about nano technology and one of the latest electronic feats was controlling the base on a transistor with one single electron.How would you like to try to setup a biasing voltage for that?

My problem with that statement was since we can't see an electron how are they sure of that,what do you think?

Ronald
 
Ronald,

It's been a while for me, as well.

The idea of a single electron base current is a little too quantum for me to understand. . .
 
By spsnyder:

For those interested, a major reason the power supply is as big as it is has to do with the substatial inductor required, but more to do with an isolation transformer required for safety.
Click to expand...

I haven't read all the responses after the isolation transformer was brought up, but I need to ask, "what transformer doesn't "isolate""? And where does the safety come from?

Good questions for an instructor even.
 
An auto-transformer (like a buck-boost) does not isolate.

Imagine if there was an internal winding to winding short (for example X1 shorts to XI2). In an isolation transformer the effect would be zero voltage out of the transformer, however in an autotransformer the effect could be the input voltage being passed directly to the output. This is probably one the primary reasons the NEC has restrictions on auto-transformers.
 
By Ronald:

Been a long time since my electronics days.Talking about the bias voltage. I read something some where the other day about nano technology and one of the latest electronic feats was controlling the base on a transistor with one single electron.How would you like to try to setup a biasing voltage for that?
Click to expand...

Isn't that a rifle Ronald? Voltage is the load behind the projectile. 8)
 
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