Questions tagged [linear-regulator]

A linear voltage or current regulator provides a continuous non-pulsed supply of current or voltage. It may be fixed or adjustable, and can be put under control by a CPU/MPU. In spite of sometimes low efficiency they are popular because they provide clean noise-free DC current or voltage, as opposed to switching supplies that can be very efficient with power regulation but induce much RF noise into the outputs which need extra parts to filter out.

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Resources to use to learn the nitty gritty details of linear voltage regulators and how to use/ build them

For my current project, I need to regulate a 12V DC power supply to 5V DC, and I've chosen to do so via a linear regulator. While tutorials exist online, they—to my knowledge—don't go over the ...
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Is a Synchronous Step-Down Converter powered from industrial 24v a good choice to power a 3.3 volt MCU and sensor ic?

I am building a sensor that will be powered from a 24v industrial power supply. The board will contain a 3.3 Volt MCU and sensor IC. Is it a good idea to use a synchronous step-down converter and just ...
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Voltage drop across power supply rail

I have multiple PCBs which are communicating via CAN and are supplied by two power sources (5V and 24V). After the first field test we noticed a considerable voltage drop at the power supply between ...
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LDO Voltage Regulator - Will there be an issue

I am working on a design that utilizes a LDO Fixed Voltage Regulator. The voltage in is 24V and expected voltage out is 3.3V. I know the part is spec'd for 24V (Vin-max) and output of 3.3V, but should ...
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LT3015 not regulating

I designed a simple circuit around LT3080 (positive linear regulator) and LT3015 (negative linear regulator). LT3015 datasheet I'm feeding them with +19V and -19V (input bypass caps not show) the ...
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Are all linear regulators bad at filtering input ripple? (or really as bad as Dave suggests)?

Background In EEVBlog #1116, Dave discusses a method to remove power supply ripple, and goes on to show (see 5:17 to 6:15) that you cannot count on linear regulators to remove your input ripple. He ...
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AC to DC power supply questions

I have built the circuit in the diagram below with a couple of minor changes. I desire 3 DC outputs - +12, -12, and +5 volts. So, the changes I made is to use an MC7812BTG for the +12 and an MC7912BTG ...
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5V LDO blowing up only when testing current draw

I have a circuit to power some 5-volt logic from a +24VDC source. It has some basic reverse-polarity protection and uses a TI 5VDC LDO. It all works great during normal operation however, when I use ...
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130 views

Best way to drop 10volts at 0.25A with linear regulator?

What would be a minimalistic circuit design to convert 14V to 3.3V at 0.25A with a linear regulator? I'm thinking about two linear regulators. I've tried LM7805(14V-5V) to LD1117(5V-3.3V.) LM7805 ...
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Positive and negative rail for op amp circuit

I need a positive and negative rail to power an op amp Since it's an op amp for a voltage reference, would using a circuit like this one be enough? Input voltage is unregulated 37 volts, with 4.7k ...
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How to wire several 78XX series regulators?

I have a 30V power source and I need to get several different voltages from it using linear regulator. 24V for op amps, 12V for relays and 5V for MCU. They all going to be installed on a heatsink. If ...
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Why Does the Input Voltage Drop When a Linear Regulator is Added as Load

Why does adding a linear regulator to this circuit cause the input voltage (V_c) to drop? The 9V input coming in is regulated. The voltage measured at the branch between D5 and R22 is ~8.7 V, so it ...
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103 views

Discrete linear voltage regulator

I am trying to make a discrete component linear power supply. This schematic seemingly works but it doesn't work when I build it on my breadboard. I am taking 110 volts through a transformer down to ...
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59 views

Controlling high voltage pulsed load

I have designed a power supply that has two outputs, one at -3kV (200mA) and one at -6kV (10mA). A new design challenge has arisen that includes the need to pulse both of the outputs from nominal load ...
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LM338 regulator resistor power rating

How do I calculate the power rating of the two 100 milliohm resistors in this circuit?
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What are the disadvantages of using a Zener diode over a linear voltage regulator?

I wonder why a Zener diode is worse than linear voltage regulator. Some of the posts online mentioned that because of the power dissipating problem. Zener diodes keep consuming a large amount of ...
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Driving 34 White LEDs in Series with Linear CC Source with 110V Mains

I have 102 White LEDs in total and I want to drive them from the 110V rectified Mains in 34S 3P configuration. Here's the graph about the LEDs (Red Line). I want to pass only about 50mA ...
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Linear power supply using LM338

I'm trying to design a linear power supply to provide 32V and up to 10 amps from a 50V source. Is this the correct way of using multiple LM338 regulators to achieve this?
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How do I tell if a voltage regulator is enough to supply a larger board?

So I'm currently designing a PCB that's fairly large by my standards (10"x5"). It's a 4-layer board with internal GND and 5V layers. I'm currently using a linear regulator (LM340SX) to provide the 5 ...
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Trying to get 2 Amps out of 3 Amp Regulator (MIC29302WU)

I am trying to get 5V,2A out of the MIC29302WU (TO-263 package) with an input voltage of 12V. The voltage drops to around 2.2V when trying to supply even 1.3A. Blowing canned air over the regulator ...
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Load current for LM317 [closed]

simulate this circuit – Schematic created using CircuitLab LM317 requires 10mA load to maintain regulation. the simplest option is to add a resistor, with a 10 ohm resistor as a load I get 16mA ...
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108 views

Controling LM317 digitally

simulate this circuit – Schematic created using CircuitLab I used OA1 as feedback for adjust pin and OA2 as a buffer, there's a 10 mA load at the output to meet the minimum load requirement of ...
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Linear regulator doesn't keep the right voltage when connected to ESP8266

I am trying to use a MCP1700-3302E LDO to regulate voltage from single-cell LiPo battery to my ESP8266 (Wemos D1 package). I intend to use the LiPo down to 3.5V, and since ESP8266 requires 3.3V, that ...
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Polarities of high current bypass, and short circuit protection, transistors on LM7912 - NPN or PNP?

With reference to Olin's answer to Connecting Voltage Regulators 7812 in Parallel for High Current, and likewise the examples from the Fairchild, TI and ST datasheets, a PNP transistor is used (i.e. ...
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252 views

Combining switching and linear regulators

If we have a 12V DC input voltage and we drop that voltage using a switching regulator (LM2596) to 9V and then use a linear regulator (7805) to drop 9V to 5V, what is the output voltage going to look ...
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ADXL354 Power Sequencing Sources and LDO's

The ADXL354 with Analog Outputs include three power pins: Analog Power Source V1P8ANA, Digital Power Source V1P8DIG and Logic ...
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133 views

Can someone explain the purpose of R53 in this old linear power supply circuit

This is an old linear power supply schematic. The 78GU1C is a four pin adjustable regulator. It adjusts its output to keep its sense pin, pin 1, at 5V. In this circuit, since there isn't a divider,...
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Adjustable LDO feedback resistor values

I'm designing a circuit using an LDO voltage regulator; specifically the LD39130SPUR from ST. This variant of the part allows for an adjustable output voltage via a potential divider as seen on page 8 ...
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1answer
149 views

LDO Heating Issue

I am working on a PCB project and having a problem with the linear regulator IC. I want to be able to maintain a relatively constant temperature for the heating element. The whole system is ...
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152 views

PNP linear regulator problem

I am designing a linear step-down regulator using a PNP pass transistor. The output of the regulator is good at no load. When I connect my regulator to a battery supply, leave it for 2 seconds and ...
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58 views

Mosfet Regulator heating issue

Guys i trying to step down voltage using mosfet. Application: Input battery supply 40 to 50 volt Output voltage is 12 volt not more than 500 ma. Mosfet heating issue due to... Since the mosfet is ...
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Transistor series regulator heating

Hi friends i am trying step down converter using transistor. Application: Micro controller power-supply = 3.3 volt Input battery supply range = 10 - 13 volt So i use BD139 for stepping down ...
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What happens to the output voltage of an unloaded linear regulator

I need a linear regulator for a project, for current sense reasons I need to select a regulator that passes its quiescent current into the load. Most regulators like this have a minimum load current ...
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107 views

Choose regulator for 12V to 5V with 3Amp [closed]

I need help on choosing type of regulator base below design requirements Design Spec: Input Voltage = 12V Output Voltage = 5V max Current = 3A Power (12-5)*3 = 21W EX: Without heat sink 60C/W (...
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116 views

Quiescent current vs GND pin current for Linear Regulator IC power dissipation

I want to confirm that, for a linear regulator IC, quiescent current multiplied by the input voltage accounts for the IC power dissipation(including drop-out voltage loss). I ask because the ...
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1500-6000V linear regulator (noise eater)

Is there any known approaches to regulate HV in the range of 1500-6000V in order to eat noise? Low-side regulation is a possibility. The idea is to get ~100V higher voltage than needed, and then ...
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Odd PCB Layout for Voltage Regulator

I am reverse-engineering a board which has a Xilinx Spartan 3E FPGA, with VCCAUX powered by a 2.5 volt regulator. Below is the PCB layout for the regulator part of the circuit, and something seems ...
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Is it possible to use 7805 regulator without capacitors at its input and output pins?

I have to drive a magnetic buzzer whose current is 50mA and max. voltage is 6V. I will use 7805 regulator to drive it as my supply voltage is variable 9V to 24V DC. There will be another small load ...
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166 views

Output capacitor in LDO regulator

I want to use an Analog Devices LDO regulator (ADP7104ARDZ-5v.) When I checked the datasheet, I found out that it requires just a 1uF capacitor on the output pin. Then I searched more and I found an ...
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24v dc High current variable speed Voltage regulator

I’m in need off a high current voltage regulator. I know a little about electronics, but not on an engineering level of designing stuff. I have a few stuff on scrap boards that I can use that lying ...
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Voltage regulator circuit

I am using this linear regulator and the application circuit looks like this: Is the above circuit good enough? I have a habit of putting a series ferrite bead on the input side but after reading a ...
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I am looking for a low power 2.5V linear regulator. Any ideas? [closed]

I'll try searching mouser and digikey but i was wondering if there was a frequently used 2.5 regulator with low quiescent current (preferably lower than 5mA). Input must be: Vin<10. I am in a bit ...
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210v DC CV/CC supply

I have an old variable power supply that consists of a multi tapped transformer, a bridge rectifier and a choke. The transformer has two sets of taps on it, 6 coarse and 6 fine, giving 36 voltage ...
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118 views

Limiting current to a LiPo battery [closed]

(Updated: Amended text. The smaller battery is a lower voltage than I originally thought.) I have a small 7.5V LiPo battery that needs a top-up charge of max (say) 500mA from a large 12V LiPo battery....
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1k views

Can't get 5V 3A DC constant

Here's the circuit I am trying to build. I want to get 5V 3A DC output but it's giving above 7V and 4A. I have checked it in the multimeter attached in the diagram. Can any one explain what's ...
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3.3V LDO Selection

If you've ever tried to find an appropriate LDO for your project you may have noticed the incredibly vast range available on the market. During my searches, I discovered this particular regulator ...
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What is the role of the transistor and diode in a soft start circuit?

Please can someone explain the purpose of both the transistor and diode in this soft start circuit
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LM317 - Calculate dissipation due to voltage drop

If I use a linear voltage regulator as LM317: Input voltage = 24 V Output voltage = 5 V (so a voltage drop of 19 V) Mean load = 480 mA (peak load = 700 mA) From the datasheet, I read that maximum ...
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290 views

Aluminum electrolytic or ceramic capacitors for linear regulator input and output?

I am using this linear voltage regulator. The datasheet indicates the input and output values for the capacitance to use, 1uF and 10uF respectively. Should these capacitors be or a particular type, ...
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wiring ac input to linear DC power supply

I have a vintage linear DC power supply. Terminals 1 and 2 are labeled just "AC input". Wanted to double check if there is a convention for which pin is hot, or if the polarity is irrelevant in this ...

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