That centre tapped coil in the Decca transmitters is there to 'soak up'
high current pulses generated in the short switching interval when both FETs
may be on together - a few ns duration. This comes about since the turn-off
time of power FETs is of longer duration than the switch on time. The 15
ohm resistor across the coil is the damping to prevent high frequency
In a SMPSU the there is a deliberate dead band generated at the cross over,
when both devices in a push pull pair are switched off, but this is
undesirable in a very high efficiency class E transmitter.
against this. The centre tapped coil for instance, loaded by
15 ohms, located
between both power FETs in the Decca 5501 PA output, seems to
me to be such a
In a certain way, my complementary bipolar PA is even showing
this basic Decca power amplifier block mentioned, such as two
transistors in a
totem pole configuration, the output employing a series
resonant circuit . . .
73 Ha-Jo, DJ1ZB>
The Information contained in this E-Mail and any subsequent correspondence
is private and is intended solely for the intended recipient(s).
For those other than the recipient any disclosure, copying, distribution,
or any action taken or omitted to be taken in reliance on such information is
prohibited and may be unlawful.