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What happens if the collector resistor breaks (its value goes to infinity) in a textbook example circuit? I assume that \$ I_C \$ hits zero, \$ U_{CE} \$ decreases until the transistor goes into saturation, but still without collector current. Does this affect the base current? Or Beta?

Thanks for the answers

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  • \$\begingroup\$ Simple : yes and yes. \$\endgroup\$ – user_1818839 Oct 21 '20 at 13:55
  • \$\begingroup\$ For three questions? \$\endgroup\$ – RobertSzili Oct 21 '20 at 13:58
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I assume that IC hits zero,

yes

UCE decreases until the transistor goes into saturation,

yes

but still without collector current. Does this affect the base current?

yes and no. It doesn't affect it much, through hre. So no, if we're dealing with a simple ideal transistor, in which that parameter is zero.

Or Beta?

Yes. Beta is only measurable when the transistor is in the linear mode. You've already established that the transistor is in saturation. With a very simple ideal transistor, you might say that the underlying 'true' beta is constant, so it's not altered by there happening to be zero collector current. However, when you look at the curves for any real transistor, beta varies with collector current, dropping off at very low and very high currents.

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  • \$\begingroup\$ Thanks, have no further questions. \$\endgroup\$ – RobertSzili Oct 21 '20 at 14:03
  • \$\begingroup\$ @Neil_UK. Why do think this device would go into saturation? Current through the B-C pn junction - even with an open collector? \$\endgroup\$ – LvW Oct 21 '20 at 14:38

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