IW3SGT 630m 5-15W amplifier (work in progress)

IW3SGT home page: www.iw3sgt.it

Here is a simple class D amplifier with an inexpensive IRF510 that costs less than 1 Euro. What does D class mean ? D class is like C class with square wave input signal. IRF510 (same for IRF520/530) requires 0-8V gate level for interdition-saturation condition but high Cin values requires a low impendance/high current driver. I use a TC428 driver by Microchip then input signal can be simple TTL signal. Why D class ? Because in MF and LF Ham use only digital mode like WSPR, OPERA, JT and slow CW (QRSS3 and more) then linearity is not necessary in the amplifier's stage that complicates the schematic and less efficiency. Have a look at this interesting document bu Paul NA5N about D, E and F class: ClassDEF1.pdf For the MOS cooling I used a surplus Intel P4 CPU heatsink, the fan is not necessary for normal operations. During long key down at 15W out (24V power supply) some capacitors become slightly warm, but I did not observe variations in the power out. I have done a test with 27, 30 and 32V and I see efficiency degradation and C10/C11 became hot.

Here is the schematics: click here or in the pictures for enlarge it .

Here the prototype: .

Microchip TC1428 driver close up .

---------------------- Prototype measurements     475kHz TTL IN        02/2015 ---------------------- power s.     power OUT ----------------------  9V 375mA        2.2W 12V 492mA        3.8W 15V 609mA        5.8W 18V 725mA        8.4W 21V 843mA       11.4W 24V 961mA       15.1W 27V 1.11A       17.8W* 30V 1.47A       20.7W* 32V 1.65A       23.0W* ---------------------- * not recommended .

Useful info IRF510 datasheet IRF520 datasheet IRF530 datasheet IRF540 datasheet TC1426 TC1427 TC1428 datasheet Mini Ring Core Calculator by DL5QWB: http://www.dl5swb.de/html/mini_ring_core_calculator.htm Elsie by Tonne Software: http://tonnesoftware.com/elsie.html .

Soon to be done: - change the MOS with IRF520/530 (target 10W at 12V) - harmonic distorsion measurement (Is a 5 pole low pass filter enough ?) - put it in a box 73 and good DX in the 630m band ! Ale IW3SGT

IW3SGT home page: www.iw3sgt.it

 

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