LDO 5V to 3.3V

Schematic
1

Hello,

I’m trying to plan and sketch an LDO (low-dropout regulator) supply circuit, where the input voltage is 5VDC, and the output voltage should be 3.3VDC, with a power of at least 3.3W.

I repeatedly encounter a problem related to a server amplifier.

I would appreciate it if I could get some help on this.

Attached is a picture of the fault and the circuit.
thanks.

Screenshot 2025-02-19 at 11.36.53
Screenshot 2025-02-19 at 11.36.532730×914 222 KB

2

LM358 is . . .

image

a Dual OpAmp . . . you have the second OpAmp not shown and not connected. You need to show it and mark the pins as not connected.

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image556×541 14.7 KB

1 Like
3

Actually it’s best if the unused OpAmp unit is connected as a voltage follower configuration or similar.
Leaving it unconnected will cause problems (noise, overheating, etc.).

Sources:

  1. I’ve been burned by this before :slight_smile:
  2. TI has a pretty good app note on this: https://www.ti.com/lit/ab/sboa204a/sboa204a.pdf?ts=1739959609657
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4

Sure, I was addressing the KiCad issue rather than the potential electronics issue :wink:

5

Does the LM358 really have enough bias current to use a zener without a resistor?

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6

There are many design errors, but I will only permit KiCad relevant discussion. This is NOT an electronics homework solution forum.

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