class AB amplifier

class AB amplifier

[‚klas ¦ā¦bē ′am·plə‚fī·ər]
(electronics)
An amplifier in which the grid bias and alternating grid voltages are such that anode current in a specific tube flows for appreciably more than half but less than the entire electric cycle.
A transistor amplifier whose operation is class A for small signals and class B for large signals.

amplifier classes

Analog amplifiers are cataloged by how much current flows during each wave cycle. Measured in degrees, 360º means current flows 100% of the time. The more current, the more inefficient and the more heat generated.

Analog



Class A
The amplifier conducts current throughout the entire cycle (360º). The Class A design is the most inefficient and is used in low-power applications as well as in very high-end stereo. Such devices may be as little as 15% efficient, with 85% of the energy wasted as heat.

Class B
The current flows only 180º for half the cycle, or two transistors can be used in a push-pull fashion, each one operating for 180º. More efficient than Class A, it is typically used in low-end products.

Class AB
Combines Class A and B and current flows for 180º to 200º. Class AB designs are the most widely used for audio applications. Class AB amplifiers are typically about 50% efficient.

Class C
Operating for less than half of one wave cycle (100º to 150º), Class C amplifiers are the most efficient, but not used for audio applications because of their excessive distortion.

Class G
A variation of the Class AB design that improves efficiency by switching to different fixed voltages as the signal approaches them.

Class H
An enhancement of the Class G amplifier in which the power supply voltage is modulated and always slightly higher than the input signal.


Current Flowing
The red indicates how much of the time current is flowing through one wave cycle.








Digital



Class D
Class D is a digital-like amplifier that works by turning a transistor fully on or off, but the "D" technically does not stand for digital. See Class D amplifier.

Class T
A variation of the Class D technique from Tripath. Class T modulates the pulses based on the individual characteristics of the output transistors.
References in periodicals archive ?
But if I was to connect a good Class AB amplifier (this the most common kind of bigger amp), you'd probably see what we were talking about.
RHA's first product in the category, the Dacamp L1 uses an ES9018K2M DAC chip and class AB amplifier for each stereo channel; a configuration which enables the processing of the highest quality digital audio files from mobile and desktop source devices.
Dan Eckersley, project engineer at Vectawave Technology, said the company had used the latest-generation LDMOS devices in the 500-W Model VBA 2700/3100-500 class AB amplifier. When used with a suitable antenna and chamber, it is capable of delivering a 600-V/m field, primarily required during 2.7-GHz to 3.1-GHz S-band automotive radar pulse EMC testing.
Then it notes that each speaker has a class AB amplifier, a kind of dual circuit that is used in some higher-quality amplifiers and car amps as well.
On the contrary, an analytical and experimental work reported in [6-8], has demonstrated an improvement of linearity of PAs designed using HT approaches over Tuned Load (TL, i.e., short circuiting harmonic terminations) class AB amplifier. Moreover, harmonic injection techniques have been proposed to optimise linearity performances [14].
where the conduction angle of a class A amplifier is 2[pi] by definition and the conduction angle of a class AB amplifier is assumed to be 3[pi]/2.
A reference class AB amplifier was also tested for comparison.
The Doherty amplifier-II (a combination of a class AB carrier amplifier and a bias-tuned class C peaking amplifier) has been compared with a class AB amplifier alone.
The model accurately represents high nonlinearities and rapid phase variations of a high power class AB amplifier. A WCDMA measurement and simulation have been conducted for verification.
Further, with efficiency so critical for battery-operated systems and designs with limited enclosure space for heat dissipation, linearization of a power-efficient class AB amplifier is a much more desirable alternative to backing off output power.
The upward sloping characteristics are the pulsed set measured about the bias point X ([V.sub.DS] = 3 V, [V.sub.GS] = -2 V) and constitute the large-signal RF characteristics the FET will follow when used as a class AB amplifier operating from a 3 V supply.