Re: heat sink

Jerry Gaffke

The impedance of a capacitor is 1/(2*pi*freq*C)
At 30mhz, a 100pf capacitor will have an impedance of 1/(2*3..14*30e6*100e-12) = 53 ohms.
The output transformer at the IRF510 drain has a 1 to 4 impedance ratio, so the drains see an impedance of 50/4 = 12.5 ohms.
So you could have significant capacitance at the drain before it loads down a 30mhz signal by very much.

On Sun, Dec 31, 2017 at 01:11 pm, Diver Martin wrote:
The IRF510's have the tab as drain, which is the RF output.  I have two IRF530's in my amplifier design on one heatsink that is grounded, have not had any issues.  You actually sometimes want a little capacitive loading on the drains sometimes to reduce the high frequency harmonics that an amplifier like this is liable to generate.

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