Transformer Selection for 85-170 MHz AC source

Hello and thanks for your time,

I would like to increase the voltage from an AC source (85 mHz to 170 mHz) from 6.3 V peak-to-peak to 28 V peak-to-peak using a transformer. In my circuit, the AC source has an output impedance of 50 ohms, and the load has an input impedance of 50 ohms.

To achieve the voltage ratio of 4.5 I believe I need an impedance ratio of ~20.

  1. Could anybody recommend a transformer that might work for my application?

  2. Should I be concerned about impedance matching reducing the power on my load due to the high impedance ratio of the transformer?

  3. If so, can you recommend a power amplifier that would maintain the 28 V peak-to-peak voltage, but increase the current across the load.

  4. Is there any other information you need to help me select an appropriate transformer?

Thank you,
Ryan

Hi Ryan,

I think it will be difficult to accomplish your goal using a transformer. The impedance matching is a primary concern, along with finding a transformer off the shelf which could even get you part way there.

You would have a better chance for success using an RF amplifier, though the design would still be quite challenging. Your output requirements would imply the need of an amplifier rated for an output power of at least 2W, assuming a sinusoidal output ((10Vrms)² / 50 Ohms = 2W).

Here are a couple of amplifiers rated for 2W or more which can handle the frequency range you specified of 85MHz to 170MHz (I am assuming you meant Megahertz (MHz) rather than millihertz (mHz) in your description, above).

RF amplifiers:

CMPA0060002F-ND
CMPA0060025F-ND

Corresponding evaluation boards:

CMPA0060002F-TB-ND for the CMPA0060002F-ND
CMPA0060025F-TB-ND for the CMPA2560025F-ND

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