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
Creating an 8x8x8 3D LED Cube: The Base PCB
Creating an 8x8x8 3D tri-color LED cube from the ground...
eetimes.com
Allocating MCU Resources Accurately
When you need a new MCU and new I/O for...
eetimes.com
Experts Call for Secure Sensors
Sensor nodes are the most vulnerable point of attack in...
eetimes.com
AMD Integrates X86, GPU & I/O
Early next year, AMD will ship Carrizo, its most integrated...
eetimes.com
Test Your Way to a Better IoT
Better design and test procedures will lead to much lower...
eetimes.com
12 Startups I Saw at Demo
The consumer Internet of Things sector is getting crowded and...
eetimes.com
Megachips: Japan's Best Kept Secret
In a recent interview with EE Times, Megachips' president and...
eetimes.com
Intel Expects 2015 Mobile Speedup
Intel is back on track with mobile, company officials said...
eetimes.com
Culture Is King in Job Search
Programmers, web developers, and software engineers often assume that technical...
eetimes.com
LEDs Go Color-Temperature & Tunable
The LED manufacturer Everlight introduced what it calls the world's...
eetimes.com
Drag An Oscilloscope Through 6km of Mud?
Sponsor Dave in the 2014 Sydney Mud Run, proceeds go...
eevblog.com
Friday Quiz: More Radar
An EE Times reader submitted our second Friday quiz about...
eetimes.com
Dick Smith – Amateur Radio & Adventure
Dick Smith talks about how he got started, the early...
eevblog.com
Want to Present a Paper at ESC Boston 2015?
If you are interested in presenting a paper on the...
eetimes.com
Transparent Car Shows Automotive's Future
TE Connectivity's clear-plastic, full-size model car shows the latest advances...
eetimes.com
Why No One Leaves Linear Technology
Why culture makes Linear Tech a winner....
eetimes.com
The Messe U-Bahn Crush Business Indicator
Electronica's healthy glow means good things for Europe's electronics sector....
eetimes.com
Automotive Industry Drives Chip Demand
Among all major end use-applications for integrated circuits, the automotive...
eetimes.com
Power Week: Duracell Buyout Tied to Wireless Power, EVs?
The acquisition of the Duracell battery brand by Warren Buffett's...
eetimes.com
What Are You Wearing?
The wearables market is at $6B this year and is...
eetimes.com
 


Privacy Statement - Copyright Information. - Contact Us

comments powered by Disqus

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

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