1kw Mosfet Linear Rf Amplifier

By :  Ir.Eliza Sukiman.MM.MA


This 1kw Mosfet Linear Rf Amplifier has made from low price Mosfets .  The MosFets are IRF 450 . They have an "on resistance" of 0.31 Ohms , will dissipate about 190W each. V dss Drain Source Voltage 500 , Id Continuous Drain Current 14 A , C iss input Capacitance 2000pF,Output Capacitance 300pF I have used them in my base station and they produce a good 1kw from 70V on 80 , 600w on  40 M .

The circuit is a Push Pull with 8 pcs for each side. The Mosfet Linear Rf Amplifier  as shown needs 75W of drive for full output. The input transformer T1 is wound on a small tubing transformer with about one turn pri. and three turns sec. The thermal sensor contact with the heat sink and well decoupled to prevent Rf pick up .The output transformer uses four large ferrite tubes . The primary is one turn of tubing transformer and the secondary is 3 turns of thinner multi strand stuff .

The power supply for this 1kw Mosfet Linear Rf Amplifier doesn't need regulating but shouldn't sag to less that 70 Volts at full load (about 25 Amps). I used a 70 Volt transformer with a 30 Amp bridge rectifier and four large 10,000uF capacitors. The standing current should be set to about 600 ma by adjusting the 10k Ohm pot . you can see . . .   schematic