Adjustable gain LNA
Low noise amplifiers are very useful. I built one with single BFG425W transistor with adjustable bias current. The schematic diagram is very simple:
LNA schematic diagram
and the PCB is 20x24mm:
LNA PCB
Archive for the ‘Amplifier’ Category.
Simple HF amplifier for QRSS beacon
This is 5 minutes soldering project. There is no schematic, just simple circuit, something between “dead bug” and conventional PCB design. I did this in two steps. First attempt was complete failure. Local OM told me that any power mosfet can operate as power amplifier for HF. Ok, maybe not just any. I tested with couple of them including IRFZ24N. Finaly I took “proper” MOSFET for higher frequency and the circuit worked pretty good:
Simple output stage for QRSS beacon assembled in “mixed” technology
I will briefly describe this quick and simple project and I hope readers would enjoy it.
Simple small QRO for HF
I followed the ARRL Homberw challenge 50 watt aplifier entry. It is low cost, simple HF linear amplifier designed and built by the author as an entry in the ARRL’s 2009 Homebrew Challenge contest. The requirements of the amplifier were: 40 meter band 50 watt output amplifier intended for use with a QRP transmitter as driver (less than 5W), constructed at a total material cost of not over $125.00.
I redesigned author original design an put it on the double sided PCB with additional output banpass filters. I started with first prototype:
