Questions tagged [lm78xx]
LM78xx are a popular series of linear voltage regulators. To name a few 7805, 7809, 7810
60 questions
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78xx adjustable voltage circuit not working
I was performing lab experiments in college and I came across "Adjustable voltage mode using 78xx" which is even mentioned in Texas Instrument's uA78xx datasheet.
But when I performed it on ...
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What is a good flyback diode for a brushed 80mm DC fan?
I have a 80mm DC brushed fan, that has a rated amp draw of 0.18A, at 12V. I am driving it with a LM7812 for positive voltage and switching with a IRLZ44N MOSFET.
I want to make sure this circuit will ...
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Output Voltage Range of a Linear Regulator
In the 5V linear regulator LM7805 datasheet, there is a voltage variation range for the 'Output Voltage' (min 4.8V, max 5.2V) parameter as can be seen in the following table. Under the 'Output Voltage'...
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Selection of heatsink and/or decreasing power
A few months back I asked a question about how to implement a voltage regulator to reduce the given rectified 33V supply voltage to about 24V. I decided to use the LM78S24 paired with a BD536 (both ...
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Can I connect two regulated power sources in series to obtain a dual power supply?
I am building two 12V regulated power supplies with LM7812. I am using a single transformer and have chosen to draw the circuits indepemdent from one another. I, however, would like to have the option ...
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Dual power supply, AC to ±12V DC, based on LM7812 + LM7912
I'd like to build a power supply, based on the LM7812 and LM7912, that outputs both +12 V and -12 V. I found this circuit online:
According to the datasheets, the LM7812 has a typical dropout voltage ...
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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 ...
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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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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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In which option, the diode will make the lm78xx circuit safer
This image was taken from Fairchild's datasheet on lm78xx. I have already built a working example of it, but I am still thinking about adding some additional diode protection (D1, D2). Which option ...
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LM7805 decoupling capacitors
Would it be possible to replace these combinations of ceramic and electrolytic capacitors with just a pair of low-ESR 10 μF ceramics?
Conversion from 12 V to 5 V, minimal consumption, only MAX485 ...
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A question about 78XX power supply design
I want to get 12V and 5V from a 24V power source. 12V drives a MOSFET H bridge and a cooling fan. 5V is for a microcontroller. I have already damaged a microcontroller due to a failed 7805 regulator.
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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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Help me understand the calculation of the current consummated by LM7805
Please help me understand how to calculate the current consummated by LM7805 during its work.
Parameters:
V(in) = 12V
V(out) = 5V
I(load) = 10mA (0.01A)
The image ...
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Can LM7805 take 30 V max as input if the load current doesn't exceed 50 mA?
Can I use a simple LM7805 for my beeper hobby circuit that monitors a 30 V battery?
The load current doesn't exceed 50 mA.
It seems the IC will dissipate (30-5)*50 mA = 1.25 W worst case.
Will the IC ...
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