# Diodes in series parallel

#### GJorf

Joined Jan 27, 2022
6
Hi, I need a little help understanding why there are two sets of three diodes in series parallel and what the resistor in parallel with the diode is doing and the capacitor at the bottom. Thanks in advance.

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#### Papabravo

Joined Feb 24, 2006
21,258
It is essentially a low pass filter that turns the square wave output of the oscillator into a piecewise approximation of a sinewave.

#### GJorf

Joined Jan 27, 2022
6
Thanks for the response. But, why use so many diodes?

#### Papabravo

Joined Feb 24, 2006
21,258
Thanks for the response. But, why use so many diodes?
It's a pretty crude approximation, more would be better. Thing of a sine with 3 steps up and 3 steps down and then the reverse. It would look kind of ugly on scope but maybe(?) sound acceptable(?).

#### GJorf

Joined Jan 27, 2022
6
But, why is the capacitor necessary at the bottom?

#### sparky 1

Joined Nov 3, 2018
768
Take 6 diodes with increasing and decreasing resistors. Each diode's resistor corresponds to a voltage at each point on the Y axis of an oscilloscope
that is:
If you divide a complete sine (360 degrees) by 6 divisions and plot the points and connect the points with straight lines you have a a piecewise approximation of the sine made of 6 segments. The more segments the smoother the line or the better the flow. The capacitor gradually stores a charge from which a sample can be taken.

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#### GJorf

Joined Jan 27, 2022
6
Thanks for all the info. Just one last question, can you explain what the resistor does in parallel with the diodes?

#### Papabravo

Joined Feb 24, 2006
21,258
Thanks for all the info. Just one last question, can you explain what the resistor does in parallel with the diodes?
When the diode conducts the resistor is "shorted". When the diode does not conduct, the resistor provides a current path.

#### GJorf

Joined Jan 27, 2022
6
Thank you. Appreciate all your responses.

#### GJorf

Joined Jan 27, 2022
6
Can someone explain the charge and discharge path of the capacitor?