Questions tagged [lm78xx]
LM78xx are a popular series of linear voltage regulators. To name a few 7805, 7809, 7810
57
questions
0
votes
2
answers
84
views
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 ...
1
vote
3
answers
2k
views
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.
...
0
votes
4
answers
440
views
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 ...
1
vote
2
answers
693
views
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 ...
1
vote
3
answers
2k
views
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 ...
1
vote
1
answer
227
views
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 ...
3
votes
1
answer
110
views
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 ...
0
votes
0
answers
41
views
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 ...
0
votes
2
answers
347
views
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 ...
0
votes
2
answers
178
views
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.
...
0
votes
2
answers
200
views
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 ...
0
votes
4
answers
289
views
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 ...
10
votes
3
answers
11k
views
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 ...
-3
votes
3
answers
505
views
Why does the LM7805 heat up? [duplicate]
I'm really not comfortable with things heating up, including this LM7805 integrated circuit wired below.
Why does this mighty LM7805 heat up?
Thank you for the help!
0
votes
2
answers
340
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 ...