I am designing a Class E power amplifier for 450MHz frequency. But how to fix the Q factor for the series LC in the output stage of the Power amplifier?
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Do you know how to read my impedance nomographs in other answers? or know how to conjugate match in Smith Charts? – Tony Stewart EE75 May 10 '17 at 18:01
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I know conjugate matching using Smith charts – Swap May 10 '17 at 18:09
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What Q do you want? also double tuned Q for wider BW? Always start with design specs , not schematic. – Tony Stewart EE75 May 10 '17 at 18:12
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In fact that is what I am having doubts on how much Q I must consider. The specs are RF input of 450 MHz, Vdd = 1.8V, output power of 1mW – Swap May 10 '17 at 18:20
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no BW spectrum? or 3OI or IP3 values or antenna Z? – Tony Stewart EE75 May 10 '17 at 18:22
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BW is from 350MHz to 500MHz. Antenna impedance is 50 ohm – Swap May 10 '17 at 18:35
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This PA is connected to the VCO of a PLL. So the input power I have to consider is the power of VCO, is it?? – Swap May 10 '17 at 18:36
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Let us continue this discussion in chat. – Swap May 10 '17 at 18:54
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How much suppression of harmonics does your country require? That sets the Q, unless you use other bandpass filters in later stages. – analogsystemsrf May 11 '17 at 04:57
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Always start with design specs , not schematic. Define all impedances, Pin, Pout, IP3, and BW.
Parallel Q is Rp/X(f) while series Q is X(f)/Rs
Thus the Load is poorly matched to the parallel tank cct and needs rearrangement or a low Z buffer to drive series tank.
Class E alternates from open circuit to low RdsOn and thus yields low Q 1st stage with Rp=RdsOn/d for duty cycle , d
Also Coss affects Cp but only during transition across Vgs=Vth
Tony Stewart EE75
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