mA7800

ali amine

Hello,

This is the user manual that I'm referring to: www.sparkfun.com/.../LM7805.pdf.

Questions:

1. What should be the input voltage of the regulator? I suppose that it should be an AC voltage. Can the voltage be a sine, square, or a triangular voltage?

2. I'm an educator in Canada. Is there a customer service tel number that I can call to discuss the 7805 regulator?

Thanks

over 4 years ago

0 LeonardEllis over 4 years ago

TI__Guru 71526 points

Hello Ali,

I'm not clear on what you are requesting. The title says mA7800, and the description references LM7805. Also the link you provided is not accessible, generates: 404 Not Found

If you are asking about the LM7805, please refer to the datasheet: https://www.ti.com/lit/ds/symlink/lm340.pdf .

Regards,

~Leonard

0 ali amine over 4 years ago in reply to LeonardEllis

Prodigy 10 points

Hi Leonard,

The part number on the chip is

JM22AQ

LM340TS

7805 P+

What should be the input voltage of the regulator? I suppose that it should be an AC voltage. Can the voltage be a sine, square, or a triangular voltage?

Thanks!

0 ali amine over 4 years ago in reply to ali amine

Prodigy 10 points

I intend on adding a full-wave rectifier at the input of the regulator to convert an AC sine signal to a DC signal.

0 Nick Butts over 4 years ago in reply to ali amine

TI__Guru 50025 points

Hi Ali,

Leonard is correct - please refer to the datasheet of the LM7805. Within it you will find all of the relevant operating specifications.

You mentioned in the original post that the input voltage should be an AC voltage. If you put a purely AC voltage at the input the device will not work. The input should be close to DC and larger than the minimum voltage in the Recommended Operating Conditions table; there can be some ripple on the input (e.g. if the input to the LDO was the output of a buck regulator or for your case a rectified AC signal), but the ripple should be roughly small-signal.

In case you are unfamiliar with how LDOs work, here is an app note that will help you understand how to use this device.

LDO Basics

Regards,

Nick

0 kai klaas69 over 4 years ago

Guru 140200 points

Hi,

the link can be opened when the last "." is removed:

https://www.sparkfun.com/datasheets/Components/LM7805.pdf

ali amine said:
What should be the input voltage of the regulator? I suppose that it should be an AC voltage. Can the voltage be a sine, square, or a triangular voltage?

The following figure shows how the input of LM7805 can be powered by the secondary winding of a mains transformer:

But, of course, you can also power the input of LM7805 by a DC voltage which is at least 2V higher than the output voltage (+5V in your case).

Kai

0 Nick Butts over 4 years ago in reply to ali amine

TI__Guru 50025 points

Hi Ali,

Is your question answered?

Thanks,

Nick

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