Why is biasing needed?

Answer 1

The function of BiasingA BJT (Bipolar Junction Transistor) require a voltage normally in the range of 0.7V for the internal junctions to become conductive. It is a fixed parameter of Silicon (Si) due to the amount of 1.1eV required to get electrons from the valence energy band into a conductive band. To be able jump the energy gap which is a forbidden band for electrons or to raise the Fermi energy level in the atom. The energy, whether it is electrically applied, thermally or optically, is required to be able change the state of a semiconductor from an insulator to an conductor. You can read more on "semiconductor theory" for better understanding.

Then with a non-linear relationship the conductivity will increase as one increase the forward bias current through the base to emitter junction. Biasing is used for classical transistor amplifier applications. Biasing is required to have the transistor half way saturated for Class-A amplification or barely switched on for Class-B power amplifiers. If a Class-B amplifier is not biased, then the lower 0.7V of the audio or sine wave will not be amplified causing crossover distortion. When you bias it correctly, the distortions will be gone, since the entire half wave will then fit into the on state of the transistor. If a Class-A amplifier is not correctly biased, premature clipping on the positive or negative part of the wave will occur.

Biasing may be used for other applications as well, such as photo transistors, internal construction of IC's such as op-amps.

Answer 2

Bipolar transistor amplifiers must be properly biased to operate correctly. In circuits made with individual devices (discrete circuits), biasing networks consisting of resistors are commonly employed. Much more elaborate biasing arrangements are used in integrated circuits, for example, bandgap voltage references and current mirrors.

The operating point of a device, also known as bias point, quiescent point, or Q-point, is the point on the output characteristics that shows the DC collector-emitter voltage (Vce) and the collector current (Ic) with no input signal applied. The term is normally used in connection with devices such as transistors.

Answer 3

Biasing is used in a transistor amplifier circuit in order to place the transistor as nearly as possible in the center of its linear region. Transistors have cutoff, linear, and saturation regions. Too little bias current, and you enter cutoff - Too much, and you saturate. Both conditions cause distortion when you attempt to use the transistor as an amplifier, as opposed to a switch. Type your answer here...

Answer 4

A: A TRANSISTOR needs to be bias to provide a DC output so when a signal need to be amplified it will be linear as opposed to clipping or distortion.