I have never put a current mirror circuit together before. Today I did, and it doesn't seem to work. I'm using a SSM2220 matched dual PNP, current mirror as seen here -
http://sub.allaboutcircuits.com/images/03282.png
when Vcc is around 12V and Rbias is 10K, I get 1.153 mA bias current. Then if the load resistor is 5.6K, I get 1.297 mA load current ? Now as I understand it, these currents are meant to be the same, but it seems whatever the values of the resistors they never are. What might be the reasons for the difference?
....also does pretty much the same thing when i simulate it, although there are loads of bugs in this simulation program...
have i misunderstood something?
http://sub.allaboutcircuits.com/images/03282.png
when Vcc is around 12V and Rbias is 10K, I get 1.153 mA bias current. Then if the load resistor is 5.6K, I get 1.297 mA load current ? Now as I understand it, these currents are meant to be the same, but it seems whatever the values of the resistors they never are. What might be the reasons for the difference?
....also does pretty much the same thing when i simulate it, although there are loads of bugs in this simulation program...
have i misunderstood something?
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