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Graph reading

post #1 of 6
3/19/03 at 3:34pm
Thread Starter 
How on earth do you read graphs like the one I've attached?? I don't know how you read the x-axis (resistance). Any help much appreciated...

g
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post #2 of 6
3/19/03 at 4:19pm
>>I don't know how you read the x-axis (resistance). <<

That is a logarithmic scale of a resistance range.

Not sure where the difficulty lies - it's simply showing how the device's quiescent current is governed by the value of resistor (R) in the circuit.
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post #3 of 6
3/19/03 at 6:54pm
Thread Starter 
its just the way the scale changes between each value of 10. And I know its a graph of quiescent current and resistance. So say for a current of 8mA, what is the corresponding resistance??

thanks, i know this sounds dumb!

g
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post #4 of 6
3/19/03 at 7:14pm
The vertical lines increment linearly in
each of the groups 10-100, 100- 1k, and 1k to 10k....

So 8ma is 200k.

14 ma is 20k

6 ma is 400 k
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post #5 of 6
3/19/03 at 7:19pm
>>for a current of 8mA, what is the corresponding resistance??<

Each increment on the Resistance (X) axis between the 100 ohm and 1000 ohm range is x*100 ohms where x is 2 - 9.

So the first 'tick' mark after 100 ohms represents 200 ohms which is where the quiescent current is 8 ma. At 400 ohms, it appears to be around 6 ma.

Log scales are used when the relationships are non-linear.
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post #6 of 6
3/19/03 at 7:25pm
Thread Starter 
ah, got it now! I'm still at high-school and we've only just started doing logarithms in maths and physics, so I'm now ahead!

thanks all

g
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