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37 votes
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What is the difference between a linear regulator and an LDO

They key property of the LDO type linear regulators is the P-type pass transistor. This allows controlling the pass transistor with a voltage below the input voltage \$V_{in}\$ for all possible output ...
tobalt's user avatar
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36 votes

What is the difference between a linear regulator and an LDO

An LDO is a type of linear regulator. All linear regulators have what's called a dropout voltage, a minimum input-to-output differential that they can't work without. The original linear regulators (...
Hearth's user avatar
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35 votes
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What is the purpose of a 1 Ω resistor to ground in the output filter of a voltage regulator?

The first easy to use 'one component' regulators to be produced, like the 7805, were NPN follower based. This meant they had a high(ish) dropout voltage. The low output impedance, and the ...
Neil_UK's user avatar
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30 votes
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Voltage regulator vs. voltage reference

A voltage regulator is designed to take a variable voltage in (say, 2-5v), and output a constant voltage (say, 3.3v). Now, voltage regulators are typically used to power a circuit, which means they ...
CHendrix's user avatar
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26 votes
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Are all linear regulators bad at filtering input ripple? (or really as bad as Dave suggests)?

In the case of the MCP1700, Dave is certainly correct. Here's the ripple rejection versus frequency chart from the datasheet: The datasheet itself claims 44dB of ripple rejection at 100Hz, which ...
JRE's user avatar
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21 votes
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Capacitors with an LDO voltage regulator - how necessary is it?

The data sheet for the regulator suggests ... How important is this? About as important as that your circuit work reliably. Trying to second-guess datasheets is a bad idea. Unless the datasheet ...
Olin Lathrop's user avatar
21 votes

Are all linear regulators bad at filtering input ripple? (or really as bad as Dave suggests)?

It doesn't entirely excuse the poor performance of the MCP1700, but I think you'll generally find that very low Iq regulators tend to have much poorer high-frequency PSRR. You would not expect an op-...
Spehro Pefhany's user avatar
19 votes
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Ferrite instead of LDO

Ferrite Beads and LDOs are typically solve two different kinds of noise problems, so very rarely will you be able to "replace" an LDO with only a Ferrite Bead. LDO's ability to filter noise is ...
Victor S's user avatar
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17 votes

LD1117v33 delivering 10 V instead of 3.3 V - what is wrong?

To be clear and to protect against changes to the question, here is your schematic: There are a number of problems here, both with the schematic and the circuit: The schematic is missing junction ...
Olin Lathrop's user avatar
15 votes
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Efficiency of a voltage regulator

Let's say I have an LDO that create 5V at 2A with an input of 10V at 1A... You have 10 W input, and 10 W output, therefore you have 100% efficiency. ...with an efficiency of 50% This is a ...
The Photon's user avatar
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14 votes

Connecting GPIOs on two boards with independent power supplies

In situations like this, I like to use an optical coupler (example) in between the two systems. The systems will remain electrically isolated, so no current will flow between them in either direction. ...
bta's user avatar
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13 votes

Voltage regulator vs. voltage reference

Generally (though there will be exceptions) references have better specifications than regulators. Included in those specifications are ... temperature stability input voltage stability output load ...
Neil_UK's user avatar
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13 votes

Are all linear regulators bad at filtering input ripple? (or really as bad as Dave suggests)?

My practice is to use a large enough capacitor before the LDO to handle high frequency ripple, with a small R or L before it if necessary, and rely on the LDO to remove the low frequency variations. ...
Neil_UK's user avatar
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12 votes

What is the difference between a linear regulator and an LDO

A low drop out regulator (LDO) is a linear regulator. Linear regulators control the output voltage by adjusting the current through an output transistor. In all linear regulators, there is a minimum ...
JRE's user avatar
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12 votes

What happens if I accidentally ground the output of an LDO regulator?

You don't currently state your VIN voltage. If your short V+ on your circuit, you're just connecting the 8.45K resistor to become a load across the regulator output. The MAX6004 has a 4.096 V output ...
TonyM's user avatar
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11 votes

LD1117v33 delivering 10 V instead of 3.3 V - what is wrong?

You certainly need a capacitor at the output. From dataheet. Stability The circuit design used in the AMS1117 series requires the use of an output capacitor as part of the device frequency ...
Bence Kaulics's user avatar
11 votes

Are all linear regulators bad at filtering input ripple? (or really as bad as Dave suggests)?

This is cherry picking functionality of a particular part. An ideal LDO has infinite PSRR so what is the limiting factor on real LDOs that degrades performance at high frequencies? I recommend you ...
EasyOhm's user avatar
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11 votes
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Is this an acceptable way to create +/-5V from +/-12V?

No. What you're calling "-5 V" would actually be +5 volts with respect to the -12 volt rail, i.e. -7 volts. And it would only be able to source current into a load returned to a lower ...
Hearth's user avatar
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10 votes
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Is creating a voltage rail loop good or bad practice?

Having low impedance on the power rail is always a good thing. So multiple power paths aren't bad in general. However a star-pattern or power plane can be better if emi is a concern. Any ripple caused ...
S_G's user avatar
  • 589
10 votes

Is creating a voltage rail loop good or bad practice?

A related peripheral issue worth being aware of: If you have analog measurement points on a board, whether internally sourced or from external sources, then at the signal levels usually dealt with by ...
Russell McMahon's user avatar
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10 votes
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Low LDO output capacitance (stability)

LDOs are feedback systems, so their stability depends on open loop gain: output voltage -> error voltage on FB pin -> internal error amp -> pass device -> output voltage. The classic ...
bobflux's user avatar
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9 votes

Voltage regulator vs. voltage reference

One additional (to your other answers) factor -- some regulators have a minimum current below which they're not specced to perform. This is similar to and may in fact be higher than the maximum ...
Chris H's user avatar
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9 votes
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Replace AMS1117 5V-3.3V LDO on NodeMCU for LiPo with low quiescent current

You choice looks good to me, but only if your NodeMCU is going to spend most of its time sleeping. In that case I'd use a MCP1700 (quiescent current < 4 uA). If it's going to spend a significant % ...
Enric Blanco's user avatar
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9 votes

Capacitors with an LDO voltage regulator - how necessary is it?

You should follow the recommendations in the datasheet. If you don't, you risk oscillation. The regulator starts to oscillate - the output goes up and down. When I've had it happen, the regulator ...
JRE's user avatar
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9 votes

At what point should I switch between a resistor divider and a LDO?

It is never a good idea to power anything from a resistor divider. Any variation on the load will change the voltage, and your MCU will very likely vary its current consumption based on what it is ...
MCG's user avatar
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9 votes
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How to reach ~50nA p-p current noise in ~200mA current source?

The main theme is: eliminate sources of 1/f as far as possible and limit bandwidth as desired. I suggest the following principal circuit (details added further down): Low Noise Resistor The main ...
tobalt's user avatar
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9 votes
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Does the HT73xx LDO regulator series have reverse polarity protection?

What happens if I feed it -10 V instead of +10 V? You will find this in the data sheet: - Basically any input voltage more negative than -0.3 volts will potentially cause it damage and, in my ...
Andy aka's user avatar
  • 460k
9 votes

Connecting GPIOs on two boards with independent power supplies

Generally speaking, as long as both boards are powered up and their power supplies are within specification for the FPGAs (e.g., ±5% or ±10%), connecting the GPIO pins directly to each other should be ...
Dave Tweed's user avatar
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8 votes

Diode Clamp failing with LDO Circuit

Alternative design concept: simulate this circuit – Schematic created using CircuitLab You may be able to eliminate R2 if the minimum draw from other circuitry is similar (a few hundred uA). ...
Spehro Pefhany's user avatar
8 votes

Difference Between RMS noise and PSRR in an LDO

The noise is internal to the LDO and is always on the output whether you power it directly from an SMPS, a battery, or the most perfect noiseless voltage source. The PSRR is how well the LDO can stop ...
DKNguyen's user avatar
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