hi all.
i want to know some basic information's about designing multistage rf transistor amplifier...
in the beginning i made 3 stage transistor(2n3904,2n3904,2n2222) 27 MHz class a amplifier, am modulation (vcc 12V),
_i amplified the rf signal from 50 mV to 400 mV,is this value good or bad?

_how is the best value of signal voltage in the 3 stage can i arrived to it?

i have transistor (2n3553) can i use it as class a transistor or power transistor?

in the power transistor, how i can calculate the RFC value that connected between vcc and collector?

i based in test on test board, is this true or false?

i think i'm heavy, but really very need to know this information's...

thank's in advance

 

Hello,

The 2N3553 will be able to give an RF output of about 2.5 Watts in class C.
I could not find any schematics where it is used as an linear amplifier.

Take a look at the PDF I posted in this post:
http://forum.allaboutcircuits.com/showpost.php?p=296945&postcount=7

Bertus

 

thank you Mr bertus, really very important informations in pdf file.
i want to ask how to know what is the value of input signal voltage or power of input signal must applied to the circuit in the 2n3553 datasheet?
it give 2.5 Watt output signal...

 

Hello,

The 2N3553 has normaly powered by an 28 Volts powersupply.
In the datasheet is given at the testapplicaion that the gain is about 10 dB,
so for 2.5 Watt output about 0.25 Watt input is needed.

You can take a look in the books of the ARRL or RSGB for schematics of RF circuits.
http://www.arrl.org/shop/ARRL-Handbook-2012-Hardcover-Edition/
http://www.rsgbshop.org/acatalog/Online_Catalogue_Technical_6.html

Bertus

 

Hello,

The 2N3553 has normaly powered by an 28 Volts powersupply.
In the datasheet is given at the testapplicaion that the gain is about 10 dB,
so for 2.5 Watt output about 0.25 Watt input is needed.

You can take a look in the books of the ARRL or RSGB for schematics of RF circuits.
http://www.arrl.org/shop/ARRL-Handbook-2012-Hardcover-Edition/
http://www.rsgbshop.org/acatalog/Online_Catalogue_Technical_6.html

Bertus

thank u Mr bertus...
i have another question please.
how i calculate input impedance for 2n3553 or 2sc2336 at 27 MHz(class e power amplifier) because there is no characteristic for input impedance in the datasheet,as you know i must make matching network..

 

Hello,

When you look at the datasheet, the power output graphs go down to 50 Mhz.
I assume the circuit will become instable below the 50 Mhz.

The use of VHF transistors is not recommeded for use at HF.
For 27 Mhz there will be other transistors available like the 2sc5739, mrf449.

This page from Advance Semiconductors might give you some more info:
http://www.advancedsemiconductor.com/transistors/rf_power_transistors.html

The pdf's on this search page might also be of any help:
http://www.ufgop.org/pdf/hf-amplifier-design/

Bertus

 

Thank you bertus