# Linear Voltage Regulator help

#### Ckoiz

Joined Sep 24, 2018
1
Hi, can anyone help me get the efficiency or any other values. This is the first time I encountered this type of linear voltage regulator so im not sure what to do.

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#### ericgibbs

Joined Jan 29, 2010
16,741
hi Ck,
Welcome to AAC.
Is this a college assignment.?
E

#### crutschow

Joined Mar 14, 2008
31,091
You question is way too general.
Have you looked at the data sheets for those regulators to try to understand what they do?

#### ebp

Joined Feb 8, 2018
2,332
Ignoring the losses due to powering a linear regulator's own circuity, the efficiency is simply Vout/Vin. For example, if the input voltage of a regulator is 9 V and the output is 5 V, the efficiency is 5/9 or 56%. You don't have to consider the current because the output current is equal to the input current, but ...

In reality, in some cases the power used by the regulator itself must be considered. If the output current is very low, the few milliamps used in the reg's circuit may be significant. With many regulators, the power they consume is more or less independent of output current. Some reg's (old low dropout voltage designs) are less efficient because some moderate fraction of input current goes to ground instead of to the output. With these reg's the power they consume is partly fixed but mostly proportional to output current.