Questions tagged [lm78xx]
LM78xx are a popular series of linear voltage regulators. To name a few 7805, 7809, 7810
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How to select proper capacitors and capacitance for LM78xx voltage regulators?
I want to use LM78xx voltage regulators for various projects. I want to know in general, how should I choose a correct value for input and output capacitors of LM78xx family when I want to change DC ...
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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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Making LM78xx fail safe against short, open, reverese bias, flyback, etc
I want to use LM78xx for various applications. What I am concerned about is its failure modes.
1. Failure to Short
Not shorting Vcc to ground!! I mean shorting V_input to V_output.
Assume that you ...
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Can I obtain a new voltage source from outputs of two cascaded linear voltage regulators in practice?
I have a device which works with 7V. I have a 7812 and 7805 already running in the circuit. Can I use the outputs of this voltage regulators to feed the 7V device?
I know this is possible in theory. ...
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Series pass transistor, LM7812
I am making a 12 volt regulator for a solar panel to power an audio amplifier. I already have a switching regulator for most application but it is very noisy for amplifier even with a lot of filtering....
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What does the CT suffix stand for in voltage regulator?
Given a regulator such as the LM7812, what does the CT suffix stand for in a voltage regulator in Fairchild LM7812CT)?
I've googled and went through the related datasheets, but could not find the ...
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LM7812 and decoupling capacitor value
LM7812 voltage regulator is recommended to be used with decoupling capacitors at its input and output as in the below diagram:
And here is the part from the manufacturer Fairchild(see recommended C1 ...
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Does the output bypass capacitor of an LM7805 double as a decoupling capacitor?
I'm using a 5v linear regulator (specifically an LM7805) that outputs directly to an ATMEGA328P. According to the LM7805 datasheet (page 23) input and output bypass capacitors should be used, as seen ...
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Connecting Voltage Regulators 7812 in Parallel for High Current [duplicate]
Could I use two L7812 voltage regulator ICs in parallel to get 12 volt and more current that with just one?
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Switch Mode Alternative to LM7805/LM7905
I am attempting to design a dual rail power supply PCB for a university project. There are a number of restrictions - namely that it maintains > 80% efficiency regardless of the current draw. I was ...
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Which capacitors to use with voltage regulator IC such as 7805?
Many of the tutorials suggest to use a large smoothing capacitor (tens and even hundreds of uF) with a full wave rectifier but the datasheets of the voltage regulators and some tutorials suggest only ...
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How much power does LM7805 dissipate?
I'm using an LM7805 in voltage regulator mode.
Vin is 15V
Vout is 5V (regulated)
The attached load draws 200mA
How to calculate how much power the LM7805 would dissipate in this setup (and whether ...
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LM7805 Voltage Drop too big
I setup the following circuit:
When I measure the voltage between GND and INPUT of the LM7805CV I have a voltage of 7.9V (around 8V as per power supply). But when I measure the output it is only 1.4V ...
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78L24 outputs high voltage >24v - Harman Kardon AVR 151
I'm trying to repair my broken Harman Kardon AVR151.
Looking at the SMPS schematic, to my very limited knowledge I do not understand,
The 78L24 is a high side 24V regulator.
Why does the schematic ...
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Suggestions for dropping resistor on LM78 regulator
I’m trying to repair a magnetic stirplate (see http://staff.washington.edu/wbeaty/chem_stir.html). I found that in one part of the circuit it fails to deliver 12V. I’ve draw part of the circuit below:
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What could have caused my power supply to fail?
I made a dual +/- 12 V power supply for synthesizer circuits using a schematic by Moritz Klein (image below). The input of the supply is from a 12 VAC transformer.
After soldering the circuit on a ...
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Do 74HCxx chips require a linear voltage generator?
Recently I've read a book that says it's absolutely necessary to use a linear voltage regulator like LM7805 in circuits that use any of 74HCxx chips (CMOS logical gates). I thought that this advice is ...
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Running Regulator Under Voltage
Is there any disadvantage to running a Linear Regulator under the minimum voltage stated in the datasheet? For instance, In the datasheet of the LM7812C2T, it says the minimuim voltage in order to to ...
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Jumper out an LM7805
I have a 5V hobby circuit that will be externally powered from a wall wart, with way less than 1 amp. For full flexibility, I'm thinking of using a simple LM7805 regulator - but that has a 7V minimum. ...
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Why 7805 regulator gives output 6 volt?
I am using 7805 and 7815 for the voltage 5 V and 15 V respectively. I provide 24 V to 7815 it is giveinng me output voltage 18.5 V instead of 15 V. According to 18.5 V to input to 7805, its output is ...
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Zener Diode vs LM78XX
To get, say 5VDC, from the AC mains, after stepping down the high AC voltage using a transformer, we have to rectify it and regulate the output DC voltage. As I have seen, there seems to be two ...
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Is a full-wave rectifier really required with a 7810 regulator?
I'm possessed of a 12-0-12 500mA transformer.
To supply a stable 10V, I seek to connect a bridge rectifier, roughly filtered with a 1000uF/50V electrolytic capacitor and a 7810.
Is a bridge, or ...
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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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Applying 5V on output pin of LM7805 while the regulator is not powered
According to the Datasheet of LM7805 (section Application and Implementation), in some scenarios a protective diode (between IN and OUT pins) is needed to protect the regulator.
Please take a look at ...
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Make a switchable steady 5 V output circuit
I am looking to make a very accurate steady 5V power supply that can be switched on and off using the digital IO pins on an Arduino. I planned to use a 9V power supply connected to a 2N2222 transistor ...
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LM7805CV output voltage drop to 2.5v after connecting load
I've made a simple linear power supply for micro-controller with a transformer and LM7805CV as seen in the picture.
LM7805CV input voltage is 35V and output without load is 5V but after connecting a ...
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Does placing additional capacitors in parallel with CJ7805 affect its performance?
I'm not sure if this is a stupid question, but I'd still prefer to ask than regret it later. I'm designing a PCB with the CJ7805 which, like the LM7805, can supply a steady 5 volts. In this case, it's ...
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Voltage regulator replacement
I have a gadget (a Sonar) that stopped working (doesn’t respond to power on, power led does not turn on) and opening it to look for the typical signs of failure I see an L7818 voltage regulator in TO-...
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Question regarding the LM7810 voltage regulator [duplicate]
Is there a simple way I can hook up this regulator to reduce the maximum output current from the 1A rating down to a 500mA maximum output without affecting the 10vdc output?
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Why is the LM7812 getting hot in this circuit?
I have made this circuit. It works fine with normal Zener diode, however when I replaced it with the LM7812 it works fine but as time passes the regulator keeps getting very hot although the load is ...
