I have also breadboarded the SSM2220P as a current mirror, not exactly the one you have, and found that mirror branch of the circuit does not mirror the Rbias branch current very well, the difference was 4X higher in the Rload branch.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 -
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?
I have breadboarded other matched transistors that did not exhibit this anomaly with differences of 15% at most. My current measurements are in the form of voltage drops across 5% tolerance resistors, so the match was pretty good.
Something peculiar with the SSM2220P. A product I purchased on EBay??
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