Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [7805]

7805 Voltage Regulator IC is a member of 78xx series of fixed linear voltage regulator ICs.

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Optimize heat sink design - connect cooling pad on PCB backside by vias

In one of my current projects I'm using an MC7805 in a D2PAK package to generate my logic supply of 5 V from an available 24 VDC supply. The current required by the circuit is 250 mA. This results in a dissipated power of the MC7805 of: \$P=(24\…
KarlKarlsom
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Why is there always a capacitor on input and output of a voltage regulator?

Looking at the datasheet I can see that the voltage regulators are not just a zenner diode inside, they are complex devices. I have noticed that there is always a capacitor at the input and another one at the output. An example is the uA7800 series…
quantum231
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Can I use two 7805 ICs in parallel to get double current capacity?

I use a 7805 for a project where the circuit needs a higher current (~2.8 A) at 5 V. So I assume that if I use both ICs in parallel I can increase the maximum current capacity. Would it work?
Ridham
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Selecting the correct input/output capacitors for a 7805

So I've got a 7805 Regulator and I've been looking it up and each website says different info. I am using an input of 12V DC 1A Wall Adapter as an input supply. www.adafruit.com Says This regulator does not require capacitors for stability. We…
Xios
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7805 voltage regulator reverse polarity

I'm working on a project for which I need to use a 7805 voltage regulator. I feed 9V to its input pin and power a 5V board with the output. However, when the board is connected to a computer, the board outputs 5V through the same cable: even if I…
EightBlueLemons
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L7805 destroyed - why?

I used a L7805 to power a Raspberry PI and it worked for about 10 seconds then started to smoke and die. L7805 is rated for 1.5A and 35V DC input. Power supply was 24V DC (was actually two plugin 12V DC 1A adapters wired in series) that was…
Peter Quiring
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What is the purpose of the 7805 output capacitor?

How does a cap on a regulator output improve transient response? Is this cap not more appropriately drawn next to the load where it is not being defeated by intervening trace inductance? Or does this output cap serve a different purpose than the…
mhz
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What is the purpose of the 7805 input capacitor?

Most 7805 datasheets specify an input capacitor of 0.33uF or so. This one (the LM340 http://www.ti.com/lit/ds/symlink/lm340-n.pdf) at least specifies that the cap is only required if the regulator is "far" from the power supply filter, without…
mhz
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How to place a 7805 voltage regulator on a breadboard?

I have this breadboard and I have started experimenting with pic micros. In doing so I have needed a 5 volt power supply. I have seen several tutorials for wiring up 5 volt regulator circuits on a breadboard, however when I try to hook up the 7805…
Markovian8261
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7805 sense resistors

In this answer, there is a schematic showing the internals of a 7805 voltage regulator, reproduced below: First of all, what is the sense pin in the first place? Every 7805 I've ever seen had three pins, Vin, Vout, and ground. Is it internally…
Hearth
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Reducing voltage drop over 7805 regulator?

I have several projects (clocks) that require 12V and 5V supply. The 5V is for TTL ICs and the 12V powers a SMPS(Switching Mode Power Supply) to give HV(High Voltage) for a tube. The 12V pulls less than 100 mA, the 5V about 400 mA. The power source…
Efram Goldberg
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Can a 7805 ever oscillate?

I see many references to input and output caps helping with "stability" and some outright references to preventing oscillation in both answers on this site, and even in some data sheets. I also have seen references saying that the 7805 is…
mhz
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LM7805 followed by LD1117-3.3

The LM7805 datasheet recommends a 0.33uF cap on the input and a 0.1uF cap on the output. The LD1117-3.3 datasheet recommends a 0.1uF cap on the input and a 10uF cap on the output. I am building a circuit that will run off the 12V battery in a bus. I…
NK2020
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Selecting input voltage for 7805

I generally use switching 12V power supplies for my circuits since they are so common, but I understand the 7805 can take a lower input voltage. If I gave the 7805 a lower input voltage (i.e. 9V), I understand there will be less heat dissipated as…
Tristan
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Voltage regulator not heating up ... How?

I connected a L7805 to a water fountain that I measured to be consuming 0.1 A at 5 V to regulate power coming in from three 5 W, 12 V solar panels connected in parallel. The regulator is not heating up at all and is doing a great job, to my…
Reuben Miro
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