What is class B amplification?
Class B amplifier is a type of power amplifier where the active device (transistor) conducts only for one half cycle of the input signal. That means the conduction angle is 180° for a Class B amplifier.
Which are the characteristics of a class B power amplifier?
The operating point is located at or very near the collector cut off voltage. The collector current flows only for one half of the cycle of the input signal. The collector current is zero when there is no input signal. The transistor dissipates no power with zero input signals.
What are the types of Class B power amplifier?
When one of the complementary transistors is positively biased, another transistor will be turned off, so it will conduct the positive signal.
- Class B Amplifier Circuit.
- Transformer Coupled Class B Push-Pull Amplifier.
- Class B Amplifier Waveform.
- Crossover Distortion.
What is the concept of a power amplifier?
A power amplifier is an electronic amplifier designed to increase the magnitude of power of a given input signal. The power of the input signal is increased to a level high enough to drive loads of output devices like speakers, headphones, RF transmitters etc.
What is class A and class B amplifier?
A class A amplifier is conducting through all the period of the signal; Class B only for one-half the input period, class C for much less than half the input period.
What is the difference between Class A and Class B amplifier?
Class A amplifiers can be made very linear, but with limited efficiency. In theory, a class A amp can achieve 50% efficiency with inductive output coupling or 25% with capacitive coupling. Class B amplifiers are subject to “crossover” distortion, but efficiency runs theoretically as high as 78.5%.
How are power amplifiers classified?
Power amplifier circuits (output stages) are classified as A, B, AB and C for linear designs—and class D and E for switching designs. The classes are based on the proportion of each input cycle (conduction angle) during which an amplifying device passes current.
What happens when class B amplifier is in a quiescent state?
What happens when class B amplifier is in a quiescent state? Explanation: When the transistor is in a quiescent state, no input is applied across the base terminal of the transistor and hence no current flows through the transistor.
What are the advantages of Class B power amplifier?
Fig 5.3. 4 Crossover Distortion
| Class B | |
|---|---|
| Advantages | Disadvantages |
| Very low standing bias current. Negligible power consumption without signal. | Creates Crossover distortion. |
| Can be used for much more powerful outputs than class A | Supply current changes with signal, stabilised supply may be needed. |
What is efficiency of Class B amplifier?
The maximum efficiency of the class B amplifier is 78.5%.
What is a class AB amplifier?
Class AB amplifiers combine Class A and Class B to achieve an amplifier with more efficiency than Class A but with lower distortion than class B. This is achieved by biasing both transistors so they conduct when the signal is close to zero (the point where class B amplifiers introduce non-linearities).
What is the efficiency of Class B power amplifier?
Class B power amplifier. Since the active device is switched off for half the input cycle, the active device dissipates less power and hence the efficiency is improved. Theoretical maximum efficiency of Class B power amplifier is 78.5%. The schematic of a single ended Class B amplifier and input , output waveforms are shown in the figure below.
What is the push-pull configuration of a Class B amplifier?
In order to compensate these problems, the push-pull configuration is introduced in class B amplifier. The circuit of a push-pull class B power amplifier consists of two identical transistors T 1 and T 2 whose bases are connected to the secondary of the center-tapped input transformer T r1.
Is the base of a single ended Class B amplifier biased?
The schematic of a single ended Class B amplifier and input , output waveforms are shown in the figure below. From the above circuit it is clear that the base of the transistor Q1 is not biased and the negative half cycle of the input waveform is missing in the output. Even though it improves the power efficiency, it creates a lot of distortion.
What is class AB power amplifier?
Class AB power amplifier. In Class AB configuration, the active elements (transistors) are slightly biased so that the conduction angle is slightly more than 180° but much less than 360°. The transistors conduct for more than a half cycle but much less than the full cycle.