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How does a diode remove crossover distortion?
Crossover Distortion Summary By applying a small base bias voltage either by using a resistive potential divider circuit or diode biasing this crossover distortion can be greatly reduced or even eliminated completely by bringing the transistors to the point of being just switched “ON”.
How can you reduce cross over distortion?
In the case of a class B/AB amplifier, crossover distortion can be reduced by using a slight forward bias in the base circuit such that the transistors are idling at a small output current. The forward bias causes the circuit to operate in class-AB mode, so both transistors are slightly on during crossover.
What do you mean by crossover distortion in power amplifiers?
Crossover distortion is the term given to a type of distortion that occurs in push-pull class AB or class B amplifiers. It happens during the time that one side of the output stage shuts off, and the other turns on.
How are diodes and capacitors used in an amplifier?
The amount of diode biasing voltage present at the base terminal of the transistor can be increased in multiples by adding additional diodes in series. This then produces an amplifier circuit commonly called a Class AB Amplifier and its biasing arrangement is given below.
How do diodes compensate for base-emitter voltage drop?
The diodes compensate for the base-emitter voltage drop of the transistors. Each transistor is run as a emitter follower. For the top (NPN) transistor, the output will be the B-E drop less than the input, and for the bottom (PNP) transistor, the output will be the B-E drop more than the input.
How much distortion do you want in a transistor?
So, how much do you want to bias the transistors from being “class B” to “class AB” to “class A” is pretty much down to how little distortion you can tolerate.
Why does a diode have a flat spot?
This flat spot is crossover distortion. It happens due to the circuit being non-linear when it is “crossing over” between using the top the transistor to drive the output to using the bottom, or vice-versa. The diodes add a offset to the input voltage for the purpose of driving each transistor.