# resistor impedance matching

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#### rocker1025

##### Newbie level 6
Hi friends.

Please anyone tell me how to calculate for impedance for the attached document.

Regards
rocker25

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#### cks3976

##### Full Member level 6
[ 330 X 470] / [330 +470] = 193 Ohms

rocker1025

### rocker1025

points: 2

#### drkirkby

##### Full Member level 6
When there is a voltage source as here (0 and 5 V), then for analysis purposes you connect them together, as a perfect voltage source has a 0 Ohm impedance. So once you do that, it becomes a simple combination of two parallel resistors. For two resitors, R1 and R2, the combination is R1*R2/(R1+R2). For n resistors in parallel, one uses the formula 1/R=1/R1 + 1/R2 + 1/R3 .... 1/Rn.

Someone else has already worked it out for you, but I thought I'd explain why his/her method is correct.

Dave

points: 2

points: 2

### rocker1025

points: 2

#### jiripolivka

##### Advanced Member level 5
cks is right. And remember to include a good blocking capacitor from the top point to ground. At RF, many people forget to use several parallel capacitors to cover from DC to a maximum frequency. A good idea is to connect 10 uF, 0.1 uF and 10 nF in parallel- this makes a good RF short.

rocker1025

points: 2