Electronics > RF, Microwave, Ham Radio

RF amplifier does not work

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Bromsnortor:
Hi, I am trying to build an oscillator with a bigger output amplitude than the oscillator itself creates. I have a collpits oscillator that generates a 200 mVpp voltage but I want my output to be bigger to drive a class E amplifier. I have tried to make a circuit that consists of a common collector then a common base to amplify and then a common collector again. I have tried to make the impedance match between the stages and I know that the last stage is not something I can build. Does anyone know how to amplify a 150 Mhz signal using this, or another circuit?

vk6zgo:

--- Quote from: Bromsnortor on June 29, 2022, 08:24:21 am ---Hi, I am trying to build an oscillator with a bigger output amplitude than the oscillator itself creates. I have a collpits oscillator that generates a 200 mVpp voltage but I want my output to be bigger to drive a class E amplifier. I have tried to make a circuit that consists of a common collector then a common base to amplify and then a common collector again. I have tried to make the impedance match between the stages and I know that the last stage is not something I can build. Does anyone know how to amplify a 150 Mhz signal using this, or another circuit?

--- End quote ---
A RC coupled amplifier will tend to run into problems at frequencies around 150MHz (or even lower), as all the load resistors will be in parallel with circuit stray capacitance, so will deliver less gain than at lower frequencies & largish value coupling capacitors tend to look like series inductors, causing still more loss of gain.
Broadband RC amplifiers at VHF need special design, including "peaking" circuits, & novel configurations to be effective.

On the other hand, if you just need gain at a single frequency, or quite a narrow range of frequencies at VHF, you would be better served to use classic RF amplifier configurations with LC resonant tuned circuits used as the device load impedances.

BigBoss:
What is your operating frequency ?? 150 MHz more or less ??
Or
You would have a strong signal around 150 MHz from an oscillator ??

That amplifier is not adequate for amplification. 150 MHz is not a negligible frequency to amplify with simple primitive transistor amplifiers. You should think to build it more seriously.
If you need an oscillator that works around 150MHz, I can post my past design here. The output level is roughly 2.6Vpp after filtering.

Bromsnortor:
I would like to see your oscillator yes.

David Hess:
C9 is crushing the output of the first emitter follower if it is connected to anything.

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