PS Component Values

[skypn]

Consider this schematic:


The section highlighted in pink is what I usually use when I only need 9vdc. Now I need both 9vdc and 4.5vdc. I searched for voltage dividers and they all looked pretty much the same. R2 and R3 always matched (I know why), and usually were 47K. C3 differed also.
My questions are; Should C1 and C3 match? How does changing their values effect the circuit? What should C2's value be?
TIA

[matmosphere]

I'm no expert but I think those are working as a voltage divider. I think in this case va is 9v and Vb depends on the value of r2 and r3. In this case I think it's 4.5 because the voltage is evenly divided between Vb and ground.

Could be wrong but that's what it looks like to me.

[Aentons]

C1,2,3 are all there to smooth out the ripple noise. Having different types and values for each helps to catch different frequencies. So it's better that they don't match. They don't effect the overall voltage output.

[skypn]

Thx guys! I'll just leave all the values alone.

[midwayfair]

C3 technically isn't even really needed if the power supply is really clean after C1, though you do want it absolutely dead silent since that 4.5V is acting as your virtual ground. C3 is just supplemental power filtering. The top leg of the voltage divider forms a low-pass filter, with 47K and a 10uF, which is easily far, far more filtering than you're getting from the few Ohms your power supply presents to the 100uF in C1.

[Aentons]

You can change the values with no I'll effects as long as you have at least C1 with a value in the uf range.  You will commonly see a 47u electrolytic and 100pf 100nf mlcc for C1 and 2. You see multiple caps of the same value in parallel alot too. For better performance, It is also recommended to use low-esr electrolytics if possible.

[aion]

You can change the values with no I'll effects as long as you have at least C1 with a value in the uf range.  You will commonly see a 47u electrolytic and 100pf mlcc for C1 and 2. You see multiple caps of the same value in parallel alot too. For better performance, It is also recommended to use low-esr electrolytics if possible.

I don't think I've ever seen a pf value for C2, it's usually either 100n or 10n... my understanding is that it's mainly just because ceramic provides better filtering at certain frequencies, so using an "average value" ceramic in conjunction with a large electrolytic, you get the best of both types. I'm not sure a 100pf capacitor would contribute much to power filtering. More often you see them on the signal input to prevent radio frequencies.

[Aentons]

You can change the values with no I'll effects as long as you have at least C1 with a value in the uf range.  You will commonly see a 47u electrolytic and 100pf mlcc for C1 and 2. You see multiple caps of the same value in parallel alot too. For better performance, It is also recommended to use low-esr electrolytics if possible.

I don't think I've ever seen a pf value for C2, it's usually either 100n or 10n... my understanding is that it's mainly just because ceramic provides better filtering at certain frequencies, so using an "average value" ceramic in conjunction with a large electrolytic, you get the best of both types. I'm not sure a 100pf capacitor would contribute much to power filtering. More often you see them on the signal input to prevent radio frequencies.

Yep, sorry, typo... You're right, 100nf.

From what I remember reading, ceramics are inherently low esr. So it's used in that position if a regular electro is used for C1.

I forget where I learned that or I'd post a link, sorry