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Class D amplifier. (translation).

Alex- Finally got what is class D amplifier (thanks for Sasha ‘s tip) – two MOSFET with similar characteristics (one is N another is P type) working as switches. Gates and drains connected, one source (P)on a power another source (N) on a ground. In simulation shows when on gates voltage low then 1.1V, then on drains is ground, and when on gates >1.1v, on drains VDD. Even gain around 8-10Db can be achieved, but it does not matter. If to skip the gain then switches will be in open or closed state, as a result PAE (Power Added Efficiency) can be around 100%. Some matching for impedance should be done, but that is a minor question. Switching voltage depend on MOSFETs, the same can be said about impedance matching design. On exits needs to put filter to make sin-cos-things.

 Simple like a Byte! Isn’t it?

Some researchers (in scientific patents) stated  that it can be important solution for low cost tooth-blue’s  power amplifier because GFSK (Gaussian Frequency Shifting Keying == shift 180 degree) less picky then π/4DQPSK (45 degree shifting) and 8DPSK(8 phases). On Wi-Fi that idea does not work.

But like in that funny story about the hunter lost direction in a forest, does not matter what you find, matter how can use it.

a) Variety MOSFETs for 2.4Ghz available only in one polarity. Maximum what can be constructed from such devices is class A, A-B (theoretical PAE 60%)

b) Check for available switches bring “Ops”. Switches working on huge frequencies with power 1-5 watts can switch from channel to channel with maximum frequency up to 1GHz (1 nanosec), and for 2.4GHz  needs to have 0.41(6) nano – Oops in full scale.

Well, what is about “space” – yep – looks like it working but topology for such chip needs to be ordered as customer’s order. Prices in that case will be around big green numbers.

With switches looks like more complicated case – restrictions on good toys is in place – you know –

What was left – (a) tubes, but needs to account power for heating, all those passive and active induct-capas-res-tors on the way into the tube and a signal's path out. (b) Traveling Wave tubes. (c) go to school to learn how transistors are working.

That’s it. Nicht gut. Today best is PAE 50% maximum, may be for Cubesat it is Ok but definitely not for the moon, solar panels on shoelaces required.

Yours truly,


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