{ I'm not at college so this isn't really a home-work question, but topic resembles a college assignment...}
How many data-points should I manually collect to make a reasonable estimate of a BJT's Early voltage ?
I know the Early voltage is the X-axis intercept extrapolation of 'active' region of Collector current vs Collector Emitter voltage for multiple Ib.
Snag is the BJTs I hope to evaluate are the Q2s of 6n139 optocouplers' split darlington.
Their data-sheet treats the device as a 'black box', for which no Q1/Q2 info or Spice model is available. Took me a LOT of research to learn that LED-->photo-diode CTR is ~0.0016 (~0.16%). I must assume that Q1 & Q2 may be optimised as pre-amp and driver, so are non-identical. I cannot do much about the 'buried' Q1 beyond back-calculating its Beta(hFE) but Q2's EBC are all accessible.
My guess would be six data-points minimum per chip, all at one Ib or as prials, with errors dropping as the sq_root of the count. I was planning to take a dozen or so readings per chip, but where should I stop ?
Measuring a dozen chips' Beta(hFE) values would give a fair guide to typical gain, but each chip's Early voltage must be extrapolated into next county...
Suggestions welcome...
How many data-points should I manually collect to make a reasonable estimate of a BJT's Early voltage ?
I know the Early voltage is the X-axis intercept extrapolation of 'active' region of Collector current vs Collector Emitter voltage for multiple Ib.
Snag is the BJTs I hope to evaluate are the Q2s of 6n139 optocouplers' split darlington.
Their data-sheet treats the device as a 'black box', for which no Q1/Q2 info or Spice model is available. Took me a LOT of research to learn that LED-->photo-diode CTR is ~0.0016 (~0.16%). I must assume that Q1 & Q2 may be optimised as pre-amp and driver, so are non-identical. I cannot do much about the 'buried' Q1 beyond back-calculating its Beta(hFE) but Q2's EBC are all accessible.
My guess would be six data-points minimum per chip, all at one Ib or as prials, with errors dropping as the sq_root of the count. I was planning to take a dozen or so readings per chip, but where should I stop ?
Measuring a dozen chips' Beta(hFE) values would give a fair guide to typical gain, but each chip's Early voltage must be extrapolated into next county...
Suggestions welcome...