Is this circuit any good for an RF amplifier?

[Resistanceisfutile]

Hello!
So I'm looking to build an amplifier for a small transmitter.
I downloaded a program called Transistor amp, their website can be visited here if you want their software:
http://en.transistoramp.de/

I entered the schematics of the circuit I wanted, and it produced this:



I'm not great with amplifiers, so I was just wondering; are these figures correct and would this be a good amplifier (ignoring the low power), for an RF circuit? Note: I already have an RF signal, I just need an amplifier circuit to improve it. I have also checked and am not breaking any laws in my country.

Edit: Sorry I just realised this belongs in the RF section.

 

[Dan Mills]

Ah, no.

That transistor will have run out of puff long before 466MHz, the collector load should probably be some sort of matching network the emitter has an AC degeneration resistor that has a silly value, and you have no impedance matching network on the base.....

So apart from EVERY part being wrong for an RF power stage it is fine.

The basic idea sort of works for a buffer amp or pre driver, but all the components are wrong and the RF version would use inductors and caps to form some kind of L match network at the collector in place of that resistor.

Get thee to a book shop for a copy of "Radio Frequency Transistors" by Dye & Granburg, or maybe a copy of "Experimental Methods in RF design", Granburg is a more theoretical coverage but it does include the design eqns, EMRFD is a more hands on approach.

I would suggest that power amplifiers at UHF make experienced engineers cry upon occasion, if you lack an RF background you will have problems.

Regards, Dan.

 

[Audioguru]

Why didn't you look at the datasheet for the transistor?? Why did you use the circuit for an audio amplifier?? Why don't you use an RF transistor in an RF circuit??
The datasheet for a BC548B transistor shows that it typically has no gain above 300MHz at 10mA (but could be 150MHz) and has no gain at a lower maximum frequency when its current is less or is more than 10mA.

 

[chuckey]

This is a funny circuit. With an undecoupled emitter resistor the gain should be Rc/Re which in this case is 2K/16K, so the voltage gain would be 1/8. I think that there are some errors in the values. I think R4 should be about 1K for Ic = 5mA and R5 should be 510 for a gain of 4. As an RF amp I do not think it would work above 30 MHZ.
Frank