L78L12

[rossbalch]

I've looked at the spec sheet for this part. I see it has a maximum input voltage of 30v. But does it have a minimum voltage?

For instance if you fed it 9v would it output 12v still? Or do you need to supply it at least 12v?

 

[rossbalch]

The reason I ask is, when I checked out the Diezel website, it says the VH4 preamp requires a 12-18v input which makes me think the regulator does not have a step up functionality.

 

[Nostradoomus]

From the datasheet

"The linear regulator input supply must be well regulated and kept at a voltage level to not exceed the maximum input to output voltage differential allowed by the device. The minimum dropout voltage (VIN – VO) must be met with extra headroom when possible to keep the output well regulated."

In layman's terms it wants to see at least 14-15v to function properly, they aren't step ups. You'd probably get around 7v if you put your 9v supply into an l12.

 

[vigilante398]

Yup, what he^ said. There are other regulators out there that are "low-drop out" (LDO), but a linear regulator like this is only ever going to be a buck regulator, which means step-down. Regulators exist which are buck-boost, meaning they can take an input lower than the output or higher than the output and still give you the correct voltage, but those are going to be more complicated switch-mode designs.

L78** regulators have a dropout voltage of 2V, which means you'll need at least 14V input to accurately get a regulated 12V output.

 

[lcipher3]

L78** regulators have a dropout voltage of 2V, which means you'll need at least 14V input to accurately get a regulated 12V output.

L78** regulators have a dropout voltage of 2V, which means you'll need at least 14V input to accurately get a regulated 12V output.

Exactly - and don't forget that whatever (transformer, etc) is feeding the 14V has to be able to deliver the power.
The transformer has to be rated for the power you will be using, and may be as high as 20v when not working hard.
Which will then drop to xxx volts the harder it has to work to power the load.

Depending on the operating voltage, current, and transformer rating and voltage - that may mean a significant amount of heat thru the 78xxx regulator.