Figure A

Figure A is the schematic of the microstrip single stage RF amplifier. The amplifier is based on the M/A-Com LF2810A MOSFET. The transistor is actually a 10 watt, 28 volt part, but provides adequate gain for this application at 12 VDC. The amplifier provides greater than 40% efficiency at the desired output power. Trimmer capacitors are used for input and output matching. Output power is adjusted by a trimpot which sets the gate bias voltage.

Figure B

Figure B is the layout for the microstrip circuit board. The board material is 0.030 inch Duroid. The circuit board is compression soldered onto a similarly sized copper heat spreader. The board and spreader are milled and drilled to accept the flange-mount transistor.

About LF2810A:

LF2810A is a RF Power MOSFET Transistor 10W, 500-1000MHz, 28V.

LF2810A Features:

• N-Channel enhancement mode device
• DMOS structure
• Lower capacitances for broadband operation
• Common source configuration
• Lower noise floor
• Applications – Broadband linear operation 500 MHz to 1200 MHz

Download LF2810A RF Power MOSFET Datasheet:

LF2810A Datasheet

1 file(s) 136.42 KB

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source: http://www.ham-radio.com/wb6zsu/components/exciter/exciter_mods.html

Schematic Diagram:

Components List:

R1 ____________________ 10R
R2 ____________________ 470R
R3 ____________________ 47R
R4 ____________________ 120R
R5 ____________________ 2K2
R6 ____________________ 4K7
R7 ____________________ 22R
Q1 ____________________ 2N2369
Q2 ____________________ 2N4427
Q3 ____________________ 78L08

C1, C11 _______________ 10n
C2 ____________________ 220u/16V
C3 ____________________ 33p
C4 ____________________ 47p
C5, C6, C7, C8, C9 ____ 1n
C10 ___________________ 10u/25V
L1 ____________________ 5 turn coil
L2 ____________________ 3 turn coil
L3 ____________________ Ferrite
L4, L5, L6 ____________ RFC

This electronic circuit is a simple 2-transistor VHF power amplifier, with about 16dB gain, and requires no tuning or alignment procedures. Wideband techniques have been used in the design and the circuit is equipped with a “lowpass” filter to ensure good output spectral purity. The project has been designed for assembly on a single-sided printed circuit board. The circuit is specifically designed to amplify the output of 7mW to 10mW WBFM transmitters (wide band) to a final level of 250mW to 300mW, after the filter.

The kit of this power amplifier circuit is available at kitsrus.com. You may download the kit manual including the information of schematic diagram, components list, and circuit works from the following link:

250mW RF Power Amplifier Manual Kit

1 file(s) 123.11 KB

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