Discussion in 'Electronics Homework Help' started by Pheezy, Sep 11, 2014.

1. ### Pheezy

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May 17, 2014
Hey all,

Attached is a circuit. I intend to calculate the impedance as indicated but I am unsure on how I would do this. The reason I need to calculate this impedance is because this is part of a bigger project where I am trying to match the source impedance with the load impedance and I will need to design a impedance matching circuit for it.

NOTE: The diodes are the BAT46WJ schottky diodes. Essentially its a rectifier with multiple stages.

Any help would be appreciated.

Cheers

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2. ### davennModerator

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1,911
Sep 5, 2009
hi pheezy

it would be handy to know which wires that cross are connected and which are not ??

get into the habit of putting "DOTS" at joint intersections

cheers
Dave

3. ### Colin Mitchell

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Aug 31, 2014
We need to know the frequency of operation, the value of the capacitors and the resistance of the LOAD.

4. ### Pheezy

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May 17, 2014
Hi Dave, I am unsure what you mean by DOTS? Any other questions regarding the circuit, ask away.

@Colin Mitchell Freq = 2.4 GHz. Assume the capacitors are in the nF range (I actually don't know yet). Once I simulate it, I will tune the capacitor values to see where I can obtain larger output voltage. Load Resistance = I thought this "whole circuit" was the load and I was calculating it. But in case you were wondering what comes at V(dc), I would say 1000 ohm resistance.

Cheers

5. ### davennModerator

13,710
1,911
Sep 5, 2009
look at a normal circuit diagram there are dots over the joint places

see this pic ....

that way you know if wires are just crossing or are also joint at that point

in your circuit ... its unknown which crossings are also joints

6. ### Pheezy

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May 17, 2014
Oh right haha. I thought DOTS was an acronym for something. But yes, I apologize. There should be dots everywhere in my diagram. There are no cross connections

7. ### Colin Mitchell

1,417
313
Aug 31, 2014
The input impedance is effectively about 1k because the capacitors are merely transferring energy from one part of the circuit to the output. The diodes are in series and only effectively produce a very small voltage drop.
The only thing you have to work out is the size of the capacitors to deliver the current.
At 2.4GHz, they can be very small to deliver a milliamp or so.

8. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
In fact, at 2.4GHz, the capacitance of the diode junctions may become quite significant.