This design originally is from Jim Veatch, WA2EUJ. As the availability of RF-Transistors in the low budget
and high frequency range is from a narrowband nature, we followed his idea and tweaked only here and there a little.
The Amplifier uses a N-Channel Enhancement-Mode Lateral MOSFET (MRF-101BN) in a Class A (Single transistor
conducts full cycle) configuration. The Operating Point was adjusted therefore, that a Bias Current of
99 mA was flowing. A Gate Voltage of approx. 2.61 V was necessary to achieve that.
The by far smartest choice was the use of the Wurth Common Mode Choke (3.3 µH 12 mΩ). This
greatly simplifies construction, as no complicated transformers need to be made. By that, the circuit becomes
highly reproduceable.
In order to sustain the high voltages (Supply : 50 V), the capacitors are rated 100 V or more.
The Gate-Bias uses a Pre-Regulator with a BCP56-10 and a Zenerdiode (15 V). The fine regulation is done
by a standard 78L05 in a SO8 case.
All resistors a 1%, 1W e.g. CR2512FX1000ELF from Bourns. (Mouser)
This Amplifier performs best with a linear Power Supply. Switching Power Supplies from the land of the rising
sun may create a comb of (unwanted) sidebands.
The final assembly. The heatsink has a 0.9 K/W which mayst get hot :-)
✈ Downloads
✈ Performance • Small Signal Gain
Output Power, Input was +19 dBm from the SMC100A.
Compression not clearly visible, but beyond + 47 dBm at the output.
My Power Supply could only deliver 3 A, which were used at + 10 dBm at the input
of the first amplifier. For this measurement, two were used in series.
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