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by baybal2 1382 days ago
> In fact, they invented a new part that has the "input" gate of an FET and the Collector-Emitter "output" of a BJT!

IGBTs are far from being a new invention.

And if we are speaking strictly, very high currents aren't switched with higher net efficiency by BJT than FET.

The reason SCR type devices are used for the kiloamperes range switches is due to them being the only switches which can mechanically/thermally handle so much current.

But for high voltages, bipolars will indeed go higher than FETs.
1 comments
marshray 1379 days ago
In "on" mode, FETs appear as a small resistance R_ds_on, but BJTs act like a mostly-constant voltage drop V_ce_sat.

So for any BJT and FET we compare, passing a current less than V_ce_sat/R_ds_on is more efficient on the FET, and for greater currents the BJT is more efficient.

link
baybal2 1377 days ago
> for greater currents the BJT is more efficient

Depending on voltage. Extremely low RDs ON FETs are there. The real world choice would depend on whether you just need a constantly open switch, or high frequency switching for power conversion.

Are you in power electronics?

link