About Armstrong Oscillator in 1GHz, 50 Ohm I/O impedance
I am working on simulation of a Armstrong Oscillator. I found a simplified schematics from Fig2.1a on Page 42, "Radio Frequency Integrated Circuits and Technologies" book as attached file.
There are some articles describe Armstrong Oscillator including RF Class C amplifier, tuned circuit, positive feedback.
I would like to start on the simulation from sub-circuit (RF Class C amplifier at 1GHz) of Armstrong Oscillator. Currently I design BJT(BFG10) common-emitter circuit as attached file. It uses two resistors to provide bias 0.65V. The voltage gain is about 5. From datasheet of BJT(BFG10)(http://www.nxp.com/documents/data_sheet/BFG10X_N.pdf), test circuit doesn't use two resistors to provide bias voltage. Does it use capacitor(C2) to provide bias?
Is RF(1GHz) amplifier design different with low frequency(2kHz) amplifier design?
Is there any useful link to design RF Class C amplifier without two resistors bias?
Thank you for your response in advance.
Best Regards,
jerry
1)This capacitor is used to ac couple or impedance matching not for biasing.
2)They have very large frequency difference of course it is different to design 1GHZ amplifier design with compare to 1khz .
3)As it is name implies they are biasing resistors they used to stabilize the bias point of the transistor.If you want you can remove them and choose appropriate configuration and calculate the resistor values for biasing transistor.Do not forget in power amplifiers biasing is very important it determines the class of power amplifier.
You should look some power amplifier design book.I recommend you to read Steve Cripps' RF Power Amplifier book.
Dear alpuslu,
Thank you for your advice.
I feel I need to learn more about RF design knowledge.
From the datasheet, it is ClassAB amplifier at 1.9GHz. I was used ClassA for low frequency(2kHz). These biases are different.
I found a Class C amplifier at 200MHz (still not fit to my project at 1GHz) from google(as attached file) as it might give me some idea about RF Class C amplifier at 1GHz.
I am gonna read the book(RF Power Amplifiers for Wireless Communications, Second Edition ~ Steve C. Cripps) to understand what is RF Class C amplifier operation and how to design.
Best Regards,
jerry