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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3answers
66 views

Transformer - 2 Wires in and 3 wires out - How to connect ground?

I have the following transformer: And the following power cable: This is for a dual-polarity power supply for some audio circuits. How should I connect the ground pin to this circuit? Can the ...
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Looking for help choosing a voltage converter / regulator for microcontroller [closed]

I am designing a board that will need 3.3 V, 2.8 V, 1.5 V, and ideally 1.2 V rails. The board will be powered by a 12 V power supply so for stepping from 12 V to 3.3 V I am planning on using a buck ...
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Arduino controlled LM350 low output voltage

I'm trying to build smart battery charger with arduino at its core. I need to somehow regulate flowing current and to do this I decided to use linear regulator LM350 and MOSFETN IRF540N. The problem ...
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178 views

What type of regulator to use? (switching or linear)

I would like to know what type of regulator is better to use in this scenario: (What is best way to convert 15V to 5V 200mAmax with lowest ripple) Vin: 15 V from isolated DC-DC converter (RS6-0515S ...
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131 views

Does the 7809 need an input bypass capacitor if it has large output capacitors in parallel?

I am using RFID aliexpresslink. RFID is suggesting this schematic: The 7809 has this schematic in the data sheet: Why is RFID power design suggesting big capacitors with low resistors? Does it mean ...
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1answer
49 views

How to test the 5 terminal regulator with multimeter?

How do I test the 5 terminal regulator (e.g. LM2575) if it's defective or not with the help of multimeter?
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143 views

Changing opamp reference in linear power supply not giving expected results

I am currently working to make a 30V 5A linear power supply and came up with this circuit so far. The circuit is supposed to give twice the reference voltage Vref. This is the output voltage that I ...
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102 views

Unexpected voltage drop in linear dual supply power regulator

I am attempting to implement a linear dual power regulator circuit using the 7805 and the 7905, as shown below. It almost works, except that the voltage difference from the ground rail to the positive ...
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919 views

Is it normal to have 3.3 V in the heat pad of a LD1117V33C linear regulator (TO-220)?

I assembled my first PCB and started measuring everything to validate that it is correct. When it was the turn of the a TO-220 linear regulator (LD1117V33C) I got surprised to see 3.3 V in the heat ...
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What is the difference between a linear regulator and an LDO

Can someone tell me what the difference between linear regulators and LDOs is? From what I have read and understood, it is that linear regulators and LDOs don't use switching elements, but I think ...
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196 views

High voltage adjustable constant current source controlled by MCU

Background: I need a microcontroller adjustable high voltage (300V) constant current. Source: High voltage boost converter. Load: Gas discharge lamp (20mA max). Can only be switch from high side. ...
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Calculating the Input Current of the LDO

I have an LDO with output specification of 1.8V and 0.45A of load current. Input voltage is 3.3V. To find out the input current, is my below calculation correct? Input Current = (1.8V * 0.45A) / 3.3V =...
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What does a Darlington pair do in a DC power supply circuit?

I really don't understand the role of the Darlington pair (T1) in this circuit. As it is a DC power supply circuit, I always thought that the pair is useful to have a high gain in audio and AOP ...
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95 views

How to configure LDO output

I am using an LDO to convert a 5V rail to 3.3V for a microcontroller. I am using the TLV707 from Texas Instruments. It gives a recommended schematic as shown here: and I have used this. I have used ...
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Bench power supply with no minimum output voltage

Just like many other electronics hobbyists, I am trying to build a variable bench power supply with 0-30 V and 0-5 A output. I have gone through various sources to get a basic idea of how to design ...
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2answers
129 views

Ultra low ripple symmetric +/-5V USB powered converter

I have a signal processing circuit that requires symmetrical +/-5V, about 0,5A each with a requirement that the output ripple should be as low as possible (ultra-low ripple.) I have tested various ...
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1answer
37 views

SP3485EN current consumption

I would like to size my source regulator for a circuit which contains the RS485 to UART bridge SP3485EN. How may I know the current consumption of the SP3485EN? Does it depend on the load? If it is, ...
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86 views

24V Bridge Rectified Relay Circuit blowing L7805 & PIC18F

I've got a circuit which is powered using a 24VAC transformer fed into a KBU606G full bridge rectifier to generate 24VDC. Originally there was a 470uF smoothing capacitor, however I was unaware that ...
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1answer
149 views

Is there any reason to use the LM317 in place of the better and more recent LM338?

This more recent version of the LM317 is fantastic, and while it happened some of my LM317s "fried" somehow, LM338s never betrayed me. Reading the datasheets, I don't find any advantage to ...
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1answer
205 views

How do I calculate the maximum load on a center-tapped AC/AC transformer for a bi-polar linear power supply with full wave rectification?

I have a 24 VCT AC to AC step-down transformer, which has three wire leads on the secondary. I'll call the secondary leads X, Y, and C, where C is the center tap. With a DMM, the voltage between X and ...
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98 views

600V DC Switch method question

I am making a linear PSU capable of O/P 600v @ 300mA. This is for vacuum tube experiments. I need to connect/disconnect the load from the PSU using a switch. I will not turn OFF the PSU itself. I ...
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Calculating base resistor value in discrete voltage regulator circuit

I am in the process of designing a split power aupply with a discrete regulator to power an integrated circuit amplifier (LM1875.) I am trying to determine the proper resistor value for the base ...
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1answer
74 views

Intuition for stability differences between PMOS and NMOS linear power supplies

Reading this question and the linked TI's LDO document led me to a more direct comparison between the two approaches: Notes: I'm using a separate V+ for the general purpose opamp to provide more ...
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88 views

Large bulk capacitance after LDO for linear power supply

I understand that modern L's need output capacitors with very low ESR and ESL for stability (or data sheet recommended values.) Is there any issue with putting a large amount (>=10000 uF) of bulk ...
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72 views

1.8kVdc to 700Vdc voltage dropper

I'm trying to get some ideas for dropping 1.8kVdc to 700Vdc using simple voltage dropping techniques/topologies. I am using a SMPS (Switched Mode Power Supply) to regulate the low voltage outputs from ...
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1answer
42 views

Question about power good connections

I have a question about power good connections. In my circuit design I'm using a LDO linear regulator (TPS79401,) an USB 3.0 controller (TUSB7320) and a Raspberry Compute Module 4. I have seen on a TI ...
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1answer
83 views

Using linear and switching regulators in parallel for servos and microcontroller

I'm just wanting to confirm that this circuit would be safe/reliable to implement. I'm hoping to run two servos - one 6V one 7.4V - in parallel with an ESP32 dev board with built-in linear regulator, ...
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5answers
528 views

Output voltage accuracy vs output ripple of a linear regulator

I am trying to select an LDO for powering the analog domain of a sensor that has a ripple requirement of < 50 mVpp @ 1.8 V. The 1.8 V LDO I intend to use has an output voltage accuracy of +/- 2% ...
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218 views

the transistor for increasing current output of linear voltage regulator

based on a suggested circuit from the datasheet, supplied current of LM7805 voltage regulator can be increased. I can't source that BD536 pnp transistor or any equivalent listed on some websites. ...
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1answer
136 views

Low noise low ripple CC/CV power supply - modern replacement for ua723cn based regulator

Recently I had opportunity to buy old Philips PE15xx series lab power supply in not bad condition for about $120, but I was too late and someone else bought it. The seller praised its very low noise, ...
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4answers
1k views

Combine two L78L05 voltage regulator to double voltage output

Is it possible to use two 5V linear regulator to get 10V output like this (I already have a bunch of 5V regulators): simulate this circuit – Schematic created using CircuitLab Are there any ...
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48 views

Does the lm317TG require a load resistor in the final design or just for testing?

I'm building variable voltage regulator, the regulator has levels of 9, 12, 15 and 18 volts and a potentiometer that allows for incremental adjustment between the levels, so at level 18v you can drop ...
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2answers
365 views

lm7905 LTSpice is not working

I have downloaded the lm7905 from this source: https://github.com/kafana/ltspice-misc/blob/master/models/regulators.lib unfortunately, it seems that the output voltage is 0mV all the time (the green ...
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1answer
74 views

Can a linear regulator be cycled on and off repeatedly without damage?

I am looking at using a linear regulator on a load that will be turned on and off once every 10 seconds(3153600 cycles per year). For context I am currently looking at L7812CV. Will this damage the ...
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1answer
110 views

AMC7135 always regulating to 30mA

I'm building a small circuit to power a heater at 380mA using a 3.7V battery. I'm using an AMC7135 to regulate the current to 380mA. Without the AMC7135 the heater would typically draw ~500mA, so ...
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1answer
86 views

Power supply protection

I'm trying to create a power supply protection (overvoltage, undervoltage, reverse polarity) for a ±33 V, 7 mA power supply for an op-amp. The opamp would be powered by a lab supply in theory. So the ...
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1answer
163 views

How do you regulate a car battery down to exactly / not more than 12V?

My problem: I want to light up the inside of transporters with a 12V LED strip. But I don't think powering it with the 12V car battery directly is a good idea. Although the name implies 12V, a car ...
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1answer
83 views

How stable should this power supply be?

I am designing a system with a variety of sub-systems. The voltage input is 24 VDC from a power supply (wall outlet). For now, I try to compose it from mostly 5 V sub-systems: SBC relays comms ...
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3answers
127 views

L78S05C only supplying 4.88 volts?

I'm working on a linear 5 V power supply for the first time. I'm using the L78S05C as I was hoping for a little elbow room on the amperage over the standard 1.5 A version. Circuit tested perfectly on ...
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146 views

LM317 Voltage Regulator

I want to regulate a voltage suppose 60 V, but I only have an LM317 (or any similar voltage regulator IC) with voltage regulation range of 30 V max. Is there any way I can use a combination of two or ...
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1answer
645 views

How to use USB 5V output for 3.3V webcam module

I want to use an old webcam module from a notebook which needs 3.3V. Therefore I want to solder it to a USB cable and use it at an USB port on my computer. For now I use the 3.3V source from a ...
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151 views

DIY power supply [duplicate]

I am trying to build a variable power supply to replace my batteries. The power supply should have a constant DC voltage just like batteries maximum current will be 10mili Amps Max voltage should be ...
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2answers
85 views

What design considerations need to be made when using switch mode power supplies and buck converters in a design?

I don't yet have a schematic but I am looking to reduce the power dissipation in linear voltage regulators in my circuit. The circuit is powered by a 24V switch mode power supply (110-240V AC to 24V ...
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1answer
70 views

Linear voltage regulator current source high side/low side regulation

My application requires a constant current source for driving LEDs across a large voltage range (60-300VDC), and also the possibility to do this on both the high side and low side of the LEDs. ...
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4answers
273 views

How safe is it to supply power to a linear regulator output?

I have a number of early-80s era microcomputers that are missing their external power supplies, or in some cases have internal power supplies that are dodgy or broken. These take various (and ...
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1answer
62 views

Additional component to linear regulator

I came across an additional circuit as shown below. There is no problem how to work as a linear regulator. But it is unclear why does the diode add? What is the purpose of this diode in circuit?
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328 views

Use a postive linear regulator for regulating a negative voltage

Can I use an LT78L05 (https://www.st.com/resource/en/datasheet/l78l.pdf), a postive voltage regulator for regulating 5V, for regulating a -5V in this configuration : simulate this circuit – ...
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1answer
98 views

Explanation and Draw of Line Impedance Stabilization Network (LISN)

I am trying to learn about LISN circuits. As far as I see, there are standards for LISN. But the point is everybody is applying standards, I would like to know why these values are chosen or why there ...
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2answers
123 views

Can I somehow make the LM7805 work hand in hand with an N-channel MOSFET to get more current out of the regulator?

I've seen the circuit with the LM7805 being used hand in hand with a PNP to provide more current. My problem is the heat that comes with said configuration. Isn't there a way to make a linear ...
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1answer
101 views

Need a minimal circuit to obtain 5V from discrete 5V to 20V (5V, 9V 12V, 15V or 20V) input

I have a Vin that can cycle between a set of discrete levels: 5V, 9V, 12V, 15V or 20V (a USB-C PD source.) The Vin will be ...

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