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simple voltage detect circuit?

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welton

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Hi,
Could some one help me to realize a simple circuit to detect a node voltage which running out of some range?
In my circuit, there is an output node of an OP, when in normal operation, it's about 1.8V~2.0 at all corners, but if the OP's feedback node is shorted to some voltage, this node will be out of this range and falls into ~VDD or ~GND.
Is there simple circuit to indicate this internal voltage is out of 1.8V~2.0V?
Thanks to everyone.
 

Hi,welton:

whats the voltage value your feedback node mabye short to?
whats the accuracy you needed?

If the accuracy is low, you can use diode connected MOSFET, provide a level
of Vth or VDD-Vth, compare with your detect voltage.

If your detect range is 1.8~2.0v, thats more complex.
it seems you need:
a bandgap, generate a vref about 1.2v,
two comperators, compares vref and 1.8*(2/3), 2.0*(3/5).

good luck!
 

Dear butterfish,
Thanks for you help.
You give me a hint to do this. Actually the accuracy is low, so I can use the method you mentioned to just use VTH and VDD-VTH to monitor if this internal voltage is running out of 1.8~2.0. Am I correct?
Thanks a lot!!
 

welton said:
Dear butterfish,
Thanks for you help.
You give me a hint to do this. Actually the accuracy is low, so I can use the method you mentioned to just use VTH and VDD-VTH to monitor if this internal voltage is running out of 1.8~2.0. Am I correct?
Thanks a lot!!

yes you are right!
please don't forget click "helped" if you really think it is helpful.:D

thanks!
 

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