A theoretical question: are there any devices out there, which don't need biassing, to handle inputs above and below zero? If not, why not? Why didn't the designer of the universe, with all its complex structures and laws, provide some way that an amplification device would just sit at a half-on half-off point on its operating curves? By itself, without biassing, I mean.

It would make life just a little bit simpler. Not much, admittedly. Or is there such a thing? One that I didn't think of?

 

A theoretical question: are there any devices out there, which don't need biassing, to handle inputs above and below zero? If not, why not? Why didn't the designer of the universe, with all its complex structures and laws, provide some way that an amplification device would just sit at a half-on half-off point on its operating curves? By itself, without biassing, I mean.

It would make life just a little bit simpler. Not much, admittedly. Or is there such a thing? One that I didn't think of?

A JFET does not require biasing.

 

A theoretical question: are there any devices out there, which don't need biasing, to handle inputs above and below zero?

An LM386 little audio power amplifier is designed to have its inputs at 0V then it does not need biasing and it does not need a negative supply voltage. Its inputs are used above and below zero.

 

An LM386 little audio power amplifier is designed to have its inputs at 0V then it does not need biasing and it does not need a negative supply voltage. Its inputs are used above and below zero.

Might be the part's only good feature.

 

The question starts a dialog in my mind. Biasing is about analog amplifiers...single supply analog amplifiers. Is there nothing in the world that doesn't require biasing? That's the same question as, "Is there any transducer which interprets a real world event into an electronic signal with a DC level which is half of my desired power supply?" Put that way, it seems the answer is, "no".

The cure, as I see it, is dual supply voltages. You can lock an input base of a bipolar transistor at zero volts DC by arranging a differential pair with the other base grounded. The rest of the requirements, idle current, gain, and frequency limitations are still a form of biasing.

@Papabravo has a good point. You can design a j-fet input amplifier which really doesn't care about what DC level the input signal contains by blocking the DC component with a capacitor. From my point of view, designing the circuit to allow for all the idle current range of any particular j-fet part number is a kind of biasing.

From my point of view, every amplifier circuit requires some kind of biasing, whether or not the input signal which contains voltage on both sides of zero. You have the right to your opinion, too.

 

I thought it was possible this was some kind of "stump the chump" riddle. Maybe the TS just plain missed the JFET era, along with Schockley diodes, unijunction transistors and tunnel diodes. If you've never seen a pangolin, it is reasonable to ask if anyone else has.

 

You're right ... I did miss the JFET era. Did most of my book learning in the 1960s, workbench learning in the 70s and 80s. Still learning today, and teaching as well! Thanks for the answers. I think my transitory curiosity has been satisfied.

 

A theoretical question: are there any devices out there, which don't need biassing, to handle inputs above and below zero? If not, why not? Why didn't the designer of the universe, with all its complex structures and laws, provide some way that an amplification device would just sit at a half-on half-off point on its operating curves? By itself, without biassing, I mean.

It would make life just a little bit simpler. Not much, admittedly. Or is there such a thing? One that I didn't think of?

Yes, there is such an amplifier device, not new and not solid state. That is the 811A triode amplifier tube, usually operated as a cathode driven linear amplifier for radio frequency signals. It is often called a "zero-bias triode.
So the fact that the laws of physics do not comply with such a silly request for removing a bit of effort in the design stages of engineering.

 

Why didn't the designer of the universe, with all its complex structures and laws, provide some way that an amplification device would just sit at a half-on half-off point on its operating curves? By itself, without biassing, I mean.

Probably because the Designer of the Universe felt it important that we learn Ohm's Law, Kirchoff's Laws, and the voltage divider formula and wanted to create some incentive for us to do so.

Or, perhaps just to separate the men from the boys.

Or, maybe he just has a perverse sense of humor and likes to watch noobs struggle.

 

Or, maybe he just has a perverse sense of humor and likes to watch noobs struggle.

All one has to do is look at the platypus... that's definite tangible proof that the man upstairs does indeed have a sense of humor.

 

The fact that we do not understand something is by no means an indication that it is wrong. Things needing bias is how we are able to adjust them to do what we want instead of what they want. Keep that in mind, because in most cases the easy and fast answer is wrong.
Consider that without friction we would all slide into the holes. ( how about THAT for both original and profound?)

 

Consider that without friction we would all slide into the holes. ( how about THAT for both original and profound?)

That's a pretty slick observation; I'll have to write it down.

 

The fact that we do not understand something is by no means an indication that it is wrong. Things needing bias is how we are able to adjust them to do what we want instead of what they want. Keep that in mind, because in most cases the easy and fast answer is wrong.
Consider that without friction we would all slide into the holes. ( how about THAT for both original and profound?)

We could just as easily slide into the poles, but only the ones on the real axis. I don't think sliding into a zero would hurt as much.