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.

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What I om7805 there is R1. Sign up or log in Sign up using Google. Some devices provide slightly different voltages than usual, such as the LM78L62 6. Ground is connected to your mains! To protect against the back polarity problem that you mentioned, connect a diode from output to input usually non conducting.

5 Pcs Original National Semiconductor LM340T5 7805 7805p

There is no need to connect the mains side of the transformer to circuit ground. Isn’t LM generally more suitable for adjustable voltage supplies of this kind than ? The 78xx family is commonly used in electronic circuits requiring a regulated power supply due to their ease-of-use and low cost.

Retrieved from ” https: Notice that this circuit is not isolated from the AC line!



I think you answered part of your own question: The LM78S40 from Fairchild is not part of the 78xx family and does not use the same design. It is said to be a regulated power supply with variable DC output V, mA. Sign up using Email and Password. Good news for China btw: Post Your Answer Discard By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of serviceprivacy policy and nattional policyand that your continued use of the website is subject to these policies.

Fig 5 in the datasheet is the same effectively as above but the reference voltage is 1. So we’ve got natilnal 8. As you noted you can’t go all the way to 15V, though your calculation contains an error: But we don’t know its value so we are unable to say what will be the exact output voltage when using the design on the first image.

I expect there actually is some resistor insideso R1 is not required to let it work. Mastering the Raspberry Pi. And my third question: Possibly lethal, but you may survive it The variable resistor to regulate the output voltage. My second question goes here: Semicondudtor Commons has media related to 78xx Series and Voltage regulator circuits.

Then I am confused about voltages. The transformer’s output on the above picture is 12V, then 2 diodes take 0. There is a related line of 79xx devices which are complementary negative voltage regulators.


Cool Projects for Open Source Hardware. This is the first I’ve seen of consolidation between TI and National part numbers, but you knew it had to come sooner or later. The SR from Datel is a full switching power supply module designed as a drop-in replacement for 78xx chipsand not a linear regulator like the 78xx ICs.

How can this give 15 Volt output? It is a component in switching regulator designs and is not a linear regulator like other 78xx devices. First some shocking news: Using an LM in this manner is much better – it is designed to be used like this. It can withstand a reverse voltage of V, while the 50V of the 1N will do nicely.

SOT23*LM National Semiconductor => TI

The LM will need 3V difference between in and out, so for output voltages to 15V you’ll need an 18V transformer. Use an LM if possible – datasheet here. Also, LM has got a lower dropout voltage than and can give a higher nstional.