After obtaining a non-smoking dummy load for my little transmitter, here's where the investigation wound up:
- Breadboard implementation (no ground plane)
- Class D operation into a resistive load (no Class E tank circuit)
- Using an SI5351A->MCP14A0601->RD15HVF1 power chain
- Using a 1 ohm resistor with an RF bead for the gate resistor (for dampening ringing on the breadboard)?
- Initial testing performed at 1 mHz with Vds configured for 9V, threshold current limited at 0.5A reduced actual supplied Vds to 8.3V
- Rise/fall times are attractive (measurement limited to <10 nS)
- BUT... MCP14A0601 dissipation is excessive (it heats up rather quickly)
Discussion: ?The MCP14A0601 data sheet () equations 4-1, 4-2 and 4-3 offer insight into the overheating. ?This chip has quick rise/fall times and is likely fine for an efficient inverter operating at 10kHz but does not appear up to the demand of an HF power chain (assuming I've correctly applied equations 4-1, 4-2 and 4-3). ?At this point in this investigation, the most attractive power chain I've constructed for the 5..10W range with potential to operate in the upper-HF region is Hans' Class D design for the QDX ().
Humor: ?Everytime I think I have a better idea, something smokes :(
73... KQ7B
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JimC (KQ7B)
