Voltage divider load-regulation characteristic

Thread Starter

halfeclipse

Joined Feb 2, 2017
11
Lab problem. They had us build a simple voltage divider with a decade box acting as the load, adjust the resistance till we saw a given current through the box (1,3,4,7 milliamps..etc), record the voltage across the load and plot that as a function of the current. It refers to this as a "load-regulation characteristic" and apparently I'm supposed to be making some sort of observation about this, but I have no clue what I'm looking at.

The relationship is linear, which is entirely expected but I'm not seeing how anything is regulated here. The overall change is quite small relative to the change in resistance needed to do so (the load voltage changing by about 4 volts took the best part of a 5k ohm difference) which seems of interest, but I have zero idea what I'm supposed to be seeing here? Googling load-regulation characteristic isn't turning up anything, at least in the context of a pure resistor circuit. Something similar is used with a zener diode, and some playing with that circuit in a sim shows a very nice very flat range for that

What is it expecting me to see here?
 

ericgibbs

Joined Jan 29, 2010
18,766
hi h,
You have answered the question in your post text.:)

If you had to say: what is the "load-regulation characteristic" of a resistive divider, what would your answer be.?

E
 

Thread Starter

halfeclipse

Joined Feb 2, 2017
11
hi h,
You have answered the question in your post text.:)

If you had to say: what is the "load-regulation characteristic" of a resistive divider, what would your answer be.?

E
So it's just looking for the linear relationship between the output current and the load voltage? And in this case the relatively high \(\frac{\Delta V_{out}}{ \Delta I_L\) (about 0.18) simply implies it's not very good at it's job?

Are you expected to find the output resistance of your voltage divider? Thevenin's Theorem?
No.
 

OBW0549

Joined Mar 2, 2015
3,566
What is it expecting me to see here?
Who knows? My guess would be the exercise might be intended to illustrate that resistive voltage dividers make terrible voltage regulators, in part because their output voltage is directly affected by load current.

You'd be surprised: every now and then we get some poor soul come in here, all bummed out because he's trying to power some low-voltage device from a higher-voltage source using a resistive voltage divider, and is sorely vexed to find that as soon as he connects his load the voltage drops drastically.
 

JoeJester

Joined Apr 26, 2005
4,390
In the days of bleeder resistors, the bleeder drew ten percent of the load current. It afforded some voltage regulation. It's not an efficient design.

In fact, the best answer in an old FCC multiple choice test on the purpose of a bleeder resistor was voltage regulation.
 
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