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bwack / C64-Saver-bwack

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Vth of Q1 2N7000 too low #13

Closed bwack closed 5 years ago

bwack commented 5 years ago

I noticed this while ordering new 2N7002 nmos transistors. They measure Vgs threshold 1.9V. The other batch I have are 2N7000 and measure 2.5V. The minimum value shown in the datasheets are below 1V (!).

The problem is the TL431. Its output is also its power supply. The output will therefor not go below 1.8-2V.

bwack commented 5 years ago

Resistor divider 33k over 82k on the N-gate seems to work fine. I will re-route the board with the new components.