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Meg ohm resistors , are opens circuits?

Gryd3

Jun 25, 2014
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So what does these Meg ohm resistors do? they just reduce the feedback voltage or current from other parallel branches or parallel paths? but why reduce it?

The Meg ohm resistors stablize the feedback voltage from drifting out of tolerance?
Are you familiar with voltage dividers?

The larger resistor in a voltage divider will drop the most voltage across it.
As you further increase that resistance, the voltage drop further increases.
No matter how much you increase that resistor, it will never drop 100% of the voltage. You can get very close though.
Once you have a reasonably large resistor in place, as you change the smaller resistor, you will realize that the voltage across the larger one hardly changes unless you change the smaller one by a large amount.

By itself, it will only limit the amount of current through part of the circuit.
When used in conjunction with other components, it can be used to help stabilize certain portions of the circuit... This is due to the fact that when using a large value resistor, the rest of the circuit can change it's current or resistance quite easily across a very wide range of values, and the voltage across the MegΩ resistor will stay stable.
It can be used in a limited sense to 'isolate' portions of circuits from each other, but this term worries me, as they are not isolated with a large value resistor, they just have a greater resistance between portions.
 

Davewalker5

Sep 20, 2014
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it can be used to help stabilize certain portions of the circuit... This is due to the fact that when using a large value resistor, the rest of the circuit can change it's current or resistance quite easily across a very wide range of values, and the voltage across the MegΩ resistor will stay stable.

True, I agree

So you're saying that the stage after it can changes it's voltage, current, resistance and it won't affect the previous stage because the Meg ohm resistor stabilizes the previous stage

The Meg ohm resistors is in series on the output of an Op amp, this helps stabilize the output or portions of the stage circuit so the next stage voltage or current is changing it won't affect the previous stage?

It can be used in a limited sense to 'isolate' portions of circuits from each other, but this term worries me, as they are not isolated with a large value resistor, they just have a greater resistance between portions.

Yes, True i agree

I think the voltage and current "looking back" won't enter the previous stage/circuit/network because the large value resistance scares it away
 

Gryd3

Jun 25, 2014
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Well. Let's be cautious on our terms.
Very high value resistors will still let voltage and current through, and by themselves will not actually do the stabilizing. It's the fact that when coupled with other very low resistance components, they will have a stable behaviour.

It's getting difficult to continue talking about though without examples. You should post another example that 'you' put together. It will help show us what you current understanding is and perhaps correct it ;)
The previous diagram you posted was only a small snippet and not enough to provide any in-depth details, as the remainder of the circuit could change the explanation.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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I think the voltage and current "looking back" won't enter the previous stage/circuit/network because the large value resistance scares it away

I think you're a troll.
 

Gryd3

Jun 25, 2014
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il_340x270.481226265_mvl6.jpg

Can you say no to that face?
 

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
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Davewalker5, have you heard the story of the blind men trying to describe an elephant, but each one touches a different part, and they all get different ideas of what an elephant is like? I feel a bit like one of those men.

You have asked a lot of questions about different parts of the same circuit. Would you like to (a) tell us what the circuit is from, and (b) post the whole circuit and any other relevant photos. This will help us to help you learn.
 
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