Duocast: can the 1N5817 diodes be swapped to 1N4148 or 1N4001 in the power section?

mimosa

mimosa

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They are Schottky with a reverse voltage of 20V; it's unclear if they are critical. Especially Vout is 27V so it seems a bit strange. Unless I don't understand their use.
 

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Solution
giovanni
The charge pump works with the diodes and capacitors network to provide ~3X the input voltage (so about 27V). However, the voltage is typically lower by about the cumulative amount of the diode’s forward voltage. The 1N5817 has a Vf of 0.45V so a total of 1.8V drop for about 25V for the actual voltage. Other diodes may have higher forward voltage (1N4148 has 1V) making them less effective for the job. They won’t break the circuit tho, I don’t think.
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The charge pump works with the diodes and capacitors network to provide ~3X the input voltage (so about 27V). However, the voltage is typically lower by about the cumulative amount of the diode’s forward voltage. The 1N5817 has a Vf of 0.45V so a total of 1.8V drop for about 25V for the actual voltage. Other diodes may have higher forward voltage (1N4148 has 1V) making them less effective for the job. They won’t break the circuit tho, I don’t think.
 
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Solution
You can substitute them, but as @giovanni said your total output voltage will be lower if the voltage drop of each diode is higher. A few circuits here use 1N4001 specifically to keep VCC slightly lower.

Each diode only sees a portion of the total multiplied output voltage across it's terminals (think of the bird on a high voltage wire analogy), so the voltage on each diode should never exceed (or even reach) the 20V maximum of a single diode.
 
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