[600MRG] Squaring circuits

[Ben Gelb]

I've now built a couple of switchmode amps (one class D and one class E) -
both use a pair of fets driven 180 degrees out of phase (class D is
push/pull, and class E has two phases that are 180 degrees out of phase
transformer coupled to the output network in series).

So for the driver, I use a mosfet driver ICs (like the IR2110, or
NCP81074A).

The mosfet drivers need 0 to 5V squarewave input (and I need a
complementary set of signals to drive each phase opposite the other).

Since I want to take sine wave input (specifically, the -3dBm K3S
transverter out), I need some kind of squaring circuit. I am really an
analog novice, so hoping some folks on this list may have some thoughts to
share on the best way to do this, or pros/cons of approach I have taken so
far.

So far I have been using a TI TL3016 high-speed comparator to produce the
input to the mosfet drivers. This comparator conveniently features
complementary outputs so it produces the signals needed to drive both
phases with correct alignment.

Input to the comparator is transformer coupled (so comparator is driven
differentially) and dc bias of 2.5V applied (to allow running comparator w/
single 5V supply).

1M feedback resistors are added between outputs and inputs to add some
hysteresis to avoid toggling during no signal condition.

Rough schematic attached.

This all seems to work ok (as evidenced by many QSOs and WSPRs on 630m) but
I wonder what other circuits folks might suggest or other design feedback
folks might have.

In particular I am a bit nervous about potential for noise getting
amplified by the comparator. I had some kind of feedback/oscillation issue
early on that i never really diagnosed, but seemed to go away after
addition of a feedline choke at the input. So have always been a bit unsure
about the robustness of this circuit...

Thanks,
Ben N1VF
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/600mrg/attachments/20180223/4adc3c43/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: squaring.PNG
Type: image/png
Size: 100324 bytes
Desc: not available
URL: <http://mailman.qth.net/pipermail/600mrg/attachments/20180223/4adc3c43/attachment.png>