Quantcast Class AB Operation

Share on Google+Share on FacebookShare on LinkedInShare on TwitterShare on DiggShare on Stumble Upon
Custom Search
 
  
 
1-7 shape and frequency. In some cases, there may be a phase difference between the input and output signal (usually 180º), but the signals are still considered to be "good copies." If the output signal is not like the input signal in shape or frequency, the signal is said to be DISTORTED. DISTORTION is any undesired change in a signal from input to output. The efficiency of an amplifier refers to the amount of power delivered to the output compared to the power supplied to the circuit. Since every device takes power to operate, if the amplifier operates for 360º of input signal, it uses more power than if it only operates for 180º of input signal. If the amplifier uses more power, less power is available for the output signal and efficiency is lower. Since class A amplifiers operate (have current flow) for 360º of input signal, they are low in efficiency. This low efficiency is acceptable in class A amplifiers because they are used where efficiency is not as important as fidelity. Class AB Operation If the amplifying device is biased in such a way that current flows in the device for 51% - 99% of the input signal, the amplifier is operating class AB. A simple class AB amplifier is shown in figure 1-5. Figure 1-5.—A simple class AB transistor amplifier. Notice that the output signal is distorted. The output signal no longer has the same shape as the input signal. The portion of the output signal that appears to be cut off is caused by the lack of current through the transistor. When the emitter becomes positive enough, the transistor cannot conduct because the base- to-emitter junction is no longer forward biased. Any further increase in input signal will not cause an increase in output signal voltage. Class AB amplifiers have better efficiency and poorer fidelity than class A amplifiers. They are used when the output signal need not be a complete reproduction of the input signal, but both positive and negative portions of the input signal must be available at the output. Class AB amplifiers are usually defined as amplifiers operating between class A and class B because class A amplifiers operate on 100% of input signal and class B amplifiers (discussed next) operate on 50% of the input signal. Any amplifier operating between these two limits is operating class AB.


Electrical News
The Next Big Thing Is The Continuum
What will come next for us? Internet of Everything, wearables,...
eetimes.com
Making EDA Exciting Again
There are still plenty of exciting challenges out there for...
eetimes.com
Turing Test -- Are You Talking to a Human or a Machine?
Imagine you are allowed to pose five questions to determine...
eetimes.com
MediaTek Cautions 'Weak Demand' for Handsets
MediaTek has pared its expectations for 2015 as a result...
eetimes.com
Patent Search Supports View 3D XPoint Based on Phase-Change
Is 3D XPoint non-volatile memory really just a version of...
eetimes.com
Industrial Automation Companies Combine
Japan's Omron is acquiring US-based Delta Tau Data Systems....
eetimes.com
Friday Quiz: Oscilloscopes
So, you use an oscilloscope every day? Well then, you...
eetimes.com
Hybrid Solar Cells Capture More
Solar cells today waste as much as 44 percent of...
eetimes.com
Google Street View Cars Test The Air
Environmental sensor firm Aclima has partnered with Google to test...
eetimes.com
Inventables X-Carve LIVE Build Part 3 + Batteriser Rant
Part 3 of Dave & David2 assembling the Inventables X-Carve...
eevblog.com
Inventables X-Carve Time Lapse Build
Time lapse footage of Dave & David 2 assembled the...
eevblog.com
Samsung's Slippage Stirs Smartphone Angst
Samsung's downbeat outlook is stirring up worries over the global...
eetimes.com
Imec, Panasonic Push Progress on ReRAM
The two companies jointly presented a paper at the recent...
eetimes.com
Patents: Exercises in Futility and Incomprehensibility?
Learning anything from patent documents has to be one of...
eetimes.com
The Best Way to Store Morse Code in C
In which we compare two approaches to store and manipulate...
eetimes.com
Test is not someone else's problem
You can reduce production time and cost if you create...
eetimes.com
NXP Touts Mixed Signal, Auto Gains
NXP Semiconductors' financial results for the second quarter of 2015...
eetimes.com
Graphene Lights Up Chips
A group of national and international researchers have demonstrated an...
eetimes.com
Independent Board Members: The Outsiders With an "In"
Being a member of the board of a hot young...
eetimes.com
Mythbusters Tests Killer Drones
See what the team on Discovery Communications' TV series Mythbusters...
eetimes.com
 


Privacy Statement - Copyright Information. - Contact Us

Integrated Publishing, Inc.
9438 US Hwy 19N #311 Port Richey, FL 34668

Phone For Parts Inquiries: (727) 755-3260
Google +