# Voltage Range Limiting

Discussion in 'The Projects Forum' started by kchrisc, Jan 12, 2013.

1. ### kchrisc Thread Starter New Member

Jan 12, 2013
2
0
Is there a way to control a voltage in a circuit so that it only passes to another part of the circuit a certain voltage range? Voltages below the low-end of the range and above the high-end are blocked?

I.e. a circuit that can use a 4V to 5V (these voltages are just examples) source but ignore anything below or above those voltages.

I've thought of JFETs and diodes to create a high-end or low-end but can't seem to workout what to use to create a usable range only.

2. ### MrChips Moderator

Oct 2, 2009
18,027
5,644
Sure. you can use zener diodes.

3. ### BillB3857 AAC Fanatic!

Feb 28, 2009
2,476
382
Easiest way would be to have voltage rails of 4.3 and 4.7 available. Like this......Or like MrChips says, use zeners.

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4. ### kchrisc Thread Starter New Member

Jan 12, 2013
2
0
Thanks for the replies however I need to constrain voltage to between a range. If the voltage supplied to this part of the circuit is below a certain point it is ignored and if it is above a certain voltage it is also ignored. I haven't had much luck in figuring this out on my own.
4v
|
|
---->4V
|
|
Pass 4 volts

4.5v
|
|
---->4.5V
|
|
Pass 4.5 volts

5v
|
|
----X0V
|
|
No pass 5 volts

Thank you.

Last edited: Jan 13, 2013
5. ### thatoneguy AAC Fanatic!

Feb 19, 2009
6,349
731
Did you see the solution in BillB3857's post? You only need to change the upper and lower voltages to change the range. Look at the output waveforms in the sim, yellow is output, green is input.

6. ### crutschow Expert

Mar 14, 2008
21,125
6,011
Do you need to have the voltage disconnected if it's above or below the limit? If so you could use a window comparator controlling a MOSFET switch.