[600MRG] Squaring circuits

[Dave Riley]

Hi Ben,

I take it that you want to stay with non linear throughput to the 
antenna but need to come up with some more gain in order to drive your 
PA input...

Surplus block gain amps are on e-bay as well as single stage mini 
circuits MMIC pills... If you do not want to run SSB then you can get 
the gain from the K3 to your PA input up even if the block gain box 
squares it off for you... I run them like that with little demise...

Here I use a simple 50 ohm high quality 'volume control' to adjust 
transverter RF gain @ 475 kcs..

But now I am trying to go linear and see that the IRFs operate very 
critical in linear mode like I need some external feedback to help the 
chain stay stable...

I hope I understood you question, nice set up you have going... I'm 
still cave ham, dead bug style here or an updated 'Junk box Jewell' like 
in an ancient QST...

73s de DaveR @ aa1a


On 2/23/2018 9:36 PM, Ben Gelb wrote:
> 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
>
>
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