How to design class c power amplifier?

[unregister]

class c 2.4 ghz amplifier

HI.
i have used PH2266(macom) to design a amplifier which output 110W,using at 2.2GHz--2.4GHz,,,,i want to simulate it,,,but there
is no model....how can i do it? any informations and suggestions
are welcome.....thanx in advance

 

[littlemmx]

amplifier fll177me

i also wanted to know whether the rf power amplifier component could used at A class and B class and so on.such as fll177me,mgf2445a,etc,usually it can be biased as A class,if i used it at B class,what will happened ?

 

[flatulent]

transistor design

Transistors in class C require high drive power. Therefore it takes a specially designed transistor to use in class C and it will produce early failure if you try to use an ordinary class A, B type transistor in class C.

Transistors designed for class C can have their bias increased to operate in class B.

Lowering the operating class decreases the efficiency and therefore increases the heat of the transistor. This should be checked for before designing the circuit. Class A is at most 50% efficient. Class B is at most 67%. If you operate at lower powers by decreasing the drive and keeping the same voltage and bias current, the efficiency is even lower.

 

[littlemmx]

a ordinary rf power amplifier,the data sheet suggests that it works at class A,i also can used it at class B through changing the bias.
That's ok?

 

[flatulent]

Yes, but the distortion will probably be greater. Class A transistors are usually designed for very low distortion needed in multicarrier service.

 

[xyz5200]

Good points !

/ Warning #2 - no thanks at elektroda!

 

[nickwang]

Do you mean transistor itself or the biased transistor by
saying "Class A/B/C transistors"?
In my opinion, it should related mostly to the bias condition, not the transistor itself.
For example, Class A means we bias the transistor to work in full period while Class B in just half period.

Comments?

 

[flatulent]

class letter

The class letter is determined by the conduction angle which is a function of bias and drive.

The design of a transistor is, like many devices and circuits, a tradeoff between many parameters that cannot all be the best at the same time.

The transistor manufacturer has a market in mind that requires some of these paramaters to be the best and the others just good. The parameters that must be the best become that way partially by the class of operation. For instance, efficiency is the worst in class A. Linearity is the best in class A.

More than 40 years ago hi if amplifiers used mostly valves/tubes. One characteristic of the design of these is that for high power operation, the 2nd and the 3rd harmonic distortion cannnot both be low at the same time. Changing the construction of the device will make one go up when the other goes down. One manufacturer designed a "push pull" tube which had low 3rd distortion and high 2nd distortion. When used in push pull circuits the 2nd from each tube cancelled because of phase and the overall distortion was low. Here is an example of a device which could have been operated in any way but was optimized for one way.

 

[mImoto]

Hi,

Read Steve Crisp book (MCU) although I bough it. You can learn quite.

Regards,

mimoto