Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

What is the difference between different classes of power amps?

Status
Not open for further replies.

elec350

Full Member level 4
Joined
Dec 17, 2006
Messages
199
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,296
Location
Iran
Activity points
2,546
hi
what is difference between different classes of power amps?
 

Kral

Advanced Member level 4
Joined
Mar 28, 2005
Messages
1,326
Helped
280
Reputation
558
Reaction score
85
Trophy points
1,328
Location
USA
Activity points
13,418
Re: help about power amp

elec350,
Assuming A sinuaoidal output:
Class A: Output device conducts for 360 degrees of the cycle
Class B: Output device conducts for 18 degrees of
. the cycle (applies to push-pull output only)
Class AB: [180 degrees] >Output device conduction angle <= [360 degrees]
Class C: Output device conduction angle is less than 180 Degrees Useful only for RF circuits where a resonant tank circuit completes the sine wave cycle. Class C amplifier can be viewed as a synchronous switch that pumps energy into the tank circuit that is tuned to the input frequency.
Class G: A scheme in which the power supply voltage automatically varies depending on the output signal amplitude. This is done to reduce the dissipation att low power outputs.
Class D: Switching amplifier that produces a pulse width modulated output at a fixed "carrier" frequency. The carrier is filtered out to produce an amplified replica of the input.
Efficiencies (listed in increasing order)
Class A (Lowest Efficency and distortion)
Class AB (Higher distortion than A, but lower than B)
Class B
Class G
Class C (Not useful for audio)
Class D
Regards,
Kral

Added after 2 minutes:

elec350
"Class B: Output device conducts for 18 degrees of " should read "Class B: Output device conducts for 180 degrees of "
 

    elec350

    Points: 2
    Helpful Answer Positive Rating

vivek_bahire

Member level 1
Joined
Aug 30, 2005
Messages
40
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,286
Activity points
1,470
Re: help about power amp

see this website:
rfic.co.uk
 

elec350

Full Member level 4
Joined
Dec 17, 2006
Messages
199
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,296
Location
Iran
Activity points
2,546
Re: help about power amp

what is the best book in this field?
 

chrisbarty

Newbie level 5
Joined
May 6, 2005
Messages
9
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,283
Activity points
1,316
help about power amp

Assuming A sinuaoidal output:
Little correction on class B
Class B: Output device conducts for 180 degrees of. Uusally used transistor pair, each conducting on one phase of the input cycle
 

Kral

Advanced Member level 4
Joined
Mar 28, 2005
Messages
1,326
Helped
280
Reputation
558
Reaction score
85
Trophy points
1,328
Location
USA
Activity points
13,418
Re: help about power amp

elec350,
Chrisbarty makes a good point about class B. Since the conduction angle is 180 degrees, the output stage must be push-pull in order to avoid severe distortion. This also applies to class AB. Distortion is not an issue for class C, since it is used to amplify an RF carrier, and the resonsnt tank circuit cleans up the waveform to produce a sine wave.
regards,
Kral
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top