Order Number LMCT. LMCT or LMCT. See NS Package Number T03B. C National Semiconductor Corporation. RRD-B30M Printed in. Semiconductors – IC – Integrated circuits – Power Management – Stabilizers FIX. Image: Click to enlarge. SOT23*LM National Semiconductor => TI. Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. Copyright , Texas Instruments Incorporated.
What I miss there is R1. I expect there actually is some resistor insideso Semiconductir is not required to let it work. But we don’t know its value so we are unable to say natjonal will be the exact output voltage when using the design on the first image.
Then I am confused about voltages. The transformer’s output on the above picture is 12V, then 2 diodes take 0. So we’ve got only 8. My second question goes here: How can this give 15 Volt output? Is it normally legal and working, does it mean that we can have any output voltage from any legal input voltage using these IC regulators?
And my third question: Isn’t LM generally more suitable for adjustable voltage supplies of this kind than ? The seems to me like a LM with those R1 and R2 added inside.
Also, LM has got a lower dropout voltage than and can give a higher current.
A can be used in an adjustable mode as per the diagram you provided – using R1 and R2, BUT it is not a good regulator to use this way as it draws substantial and variable current via its adj ground usually pin which leads to poor regulation.
Using an LM in this manner is much better – it is designed to be used semiconductlr this.
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Use an LM if possible – datasheet here. Fig 5 in the datasheet is the same effectively as above but the reference voltage is 1. To protect against the back polarity problem that you mentioned, connect a diode from output to input usually non conducting.
First some shocking news: That’s right, the standard linear regulator since many moons. The variable resistor to regulate the output voltage.
As you noted you can’t go all the way to 15V, though your calculation contains an error: You’re right about the voltage drops, though I would calculate with 1V per diode. This natkonal your regulator won’t go higher than You’ll also have to account for the ripple across the smoothing capacitor.
Here you can calculate ripple as a function of input voltagecapacitance, and load. You’ll be able to regulate from 1. In the datasheet for the LM the LM is recommended as a variable output alternative. The LM will need 3V difference between in and out, so for output voltages to 15V you’ll need an 18V transformer. The 1N for the semicondctor is overkill.
Home Questions Tags Users Unanswered. Is this based design correct? I found this design on internet: I am asking because it doesn’t correspond to the the datasheet: Al Kepp 1, 5 19 I think you answered part of your own question: Natiional that this circuit is not isolated from the AC line! There is no need to connect the mains side of the transformer to circuit ground.
The circuit is wrong. Russell McMahon k 9 There are some problems with the design. Ground is connected to your mains! Possibly lethal, but you may survive it The variable resistor to regulate the output voltage. Wow, when did LM become obsolete?
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Good news for China btw: My life will never be the same again: Reports of the death of the may be premature: This is the first I’ve seen of consolidation l7805 TI and National part numbers, but you knew it had to come sooner or later.
After human innihilate the planet in a nuclear fireball, the only thing left will be cockroaches and regulators.
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