Definition of "Bias" from the web..........."Bias is a natural leaning or preference for or against something"
As I fumble through learning electronics repair by restoring old amplifiers and searching for guidance in the diyAudio forums, I encounter the term "Bias" often. "Measuring the Bias" and "setting the Bias" is something I can do but I am still having a hard time wrapping my head around the concept. I have several electronics books and none of them give a definition of "Bias".
Is there another word or phrase that could be used in the place of "Bias" in electronics?
Does "setting the Bias" always work like a balance control between two points?
Is "Bias" always DC voltage?
As I fumble through learning electronics repair by restoring old amplifiers and searching for guidance in the diyAudio forums, I encounter the term "Bias" often. "Measuring the Bias" and "setting the Bias" is something I can do but I am still having a hard time wrapping my head around the concept. I have several electronics books and none of them give a definition of "Bias".
Is there another word or phrase that could be used in the place of "Bias" in electronics?
Does "setting the Bias" always work like a balance control between two points?
Is "Bias" always DC voltage?
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The internet calls it "biasing" ...
https://en.wikipedia.org/wiki/Bipolar_transistor_biasing
https://www.electronics-tutorials.ws/amplifier/transistor-biasing.html
https://en.wikipedia.org/wiki/Bipolar_transistor_biasing
https://www.electronics-tutorials.ws/amplifier/transistor-biasing.html
Bias in a transistor or tube is a DC current that continuously flows in the device, when there is no signal.
The bias current allows an undistorted signal to be made, and for it to be able to change in both directions.
If there were no bias current, the signal would be very distorted (rectified).
The bias current can be interpreted in terms of a DC voltage, for example a resistor that the DC bias current flows through
develops a DC voltage across it. Measuring this DC bias voltage is a proxy for measuring the DC bias current.
Or in a tube, the DC bias voltage at the grid can set the DC bias cathode current (as in a fixed bias tube output stage).
As an analogy, the static air pressure can be thought of as a bias. Sounds cause this static air pressure bias to fluctuate
more positive and more negative than the ambient pressure.
The bias current allows an undistorted signal to be made, and for it to be able to change in both directions.
If there were no bias current, the signal would be very distorted (rectified).
The bias current can be interpreted in terms of a DC voltage, for example a resistor that the DC bias current flows through
develops a DC voltage across it. Measuring this DC bias voltage is a proxy for measuring the DC bias current.
Or in a tube, the DC bias voltage at the grid can set the DC bias cathode current (as in a fixed bias tube output stage).
As an analogy, the static air pressure can be thought of as a bias. Sounds cause this static air pressure bias to fluctuate
more positive and more negative than the ambient pressure.
Thanks fubar3 and rayma, this gives me something more tangible to think about.
rayma, if I'm understanding your explanation correctly, in an audio amplifier for instance, since bias is DC current, I'm assuming it originates from the power supply
rayma, if I'm understanding your explanation correctly, in an audio amplifier for instance, since bias is DC current, I'm assuming it originates from the power supply
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Maybe you'd like "idle current" better. It's the current flowing through the output stage when doing nothing, IOW, idling.
Setting the bias in power amplifiers can often be the same as adjusting the idle current or check the quiscent current in the output transistors.
But it can also be to adjust the DC offset at the speaker terminals.
.
But it can also be to adjust the DC offset at the speaker terminals.
.
Sure, all the power used in the amp comes from the power supply (unless there's a battery ).
Vacuum tubes need to conduct a small amount of current when no signal is passing through them, sort of like an internal combustion engine that needs to keep idling when the car is not moving while driving. So, the term bias just refers to this idling current when the tube is passing no signal. If the tube were to completely stop conducting during no signal conditions, then large amount of distortion would occur as the tube goes into and out of cutoff, or no current condition. Drawing a continuous small amount of plate current prevents that from happening.
I think it’s also called a bias because it pushes the devices (hopefully) into their linear operating regions.