Explanations on a simple power section.

Frequently asked questions regarding powering your pedal.

Explanations on a simple power section.

Postby rockerpaluza » 12 Jul 2010, 14:15

can somebody help explain about this circuit?
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Last edited by lolbou on 12 Jul 2010, 14:26, edited 1 time in total.
Reason: Topic renamed for clarity and moved to FAQs
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Re: what is the use of this circuit?

Postby lolbou » 12 Jul 2010, 14:25

It's a power section (no audio in there).

D7: reverse DC supply polarity protection.
C21: cleans any AC from DC input (more filtering)
R25-R26: voltage divider to get half the DC supply for biasing purposes.
C22: decoupling cap that filters any AC from the Vr circuit to ground.

Hope that's what you're after... :wink:
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Re: Explanations on a simple power section.

Postby rockerpaluza » 12 Jul 2010, 15:31

thanks..this is what i'm after.. :D

just few more question..
1. for D7, does it means that if the DC supply is -ve, the circuit will be short-circuited through D7?
2. for R25&R26, is there any effect if i change the resistor to another value?ie 5k for both resistor?
3. for C22, where does this AC is coming from?is it from the DC supply or the VR circuit?
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Re: Explanations on a simple power section.

Postby lolbou » 12 Jul 2010, 17:28

rockerpaluza wrote:1. for D7, does it means that if the DC supply is -ve, the circuit will be short-circuited through D7?


Spot on! Imagine you plug the wrong adapter with positive voltage inside the plug and negative outside the plug (the opposite from the Boss-PSA ones), then D7 shorts to prevent any further damage.

rockerpaluza wrote:2. for R25&R26, is there any effect if i change the resistor to another value?ie 5k for both resistor?


You'll get the same Vr with two 5k resistors. See these at GEO and analog.com for further tips. You need to consider your current draw and supply type (battery or wall-wart).

rockerpaluza wrote:3. for C22, where does this AC is coming from?is it from the DC supply or the VR circuit?


It comes from the opamp's power supply itself (there's an AC current draw because of its AC activity).
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Re: Explanations on a simple power section.

Postby rockerpaluza » 12 Jul 2010, 19:56

for C22,do you mean the op-amp is coming from external circuit(VR node)?
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