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I have a table of values given to me which contains drain current Id (in μA) and gate voltage (in volts) calculated in the saturation region for a thin film transistor.

I need to find the threshold voltage by drawing a graph. I used Desmos to draw the graph based on the given values.

I know that threshold voltage is defined as the gate voltage at which a device starts to conduct, but I'm confused as to which gate voltage I should consider.

enter image description here

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  • \$\begingroup\$ Are you sure that X axis is in volts? \$\endgroup\$
    – John D
    Oct 28, 2022 at 19:32
  • \$\begingroup\$ @JohnD Yes, it is in volts but maybe a printing mistake and actually it is in millivolts. But still, which point to consider? \$\endgroup\$
    – blackblade
    Oct 29, 2022 at 9:58
  • \$\begingroup\$ "I know that threshold voltage is defined as the gate voltage at which a device starts to conduct," If starting of conduction is where the \$I_d\$ first exceeds 0 \$\mu\$A then where is that on your graph? \$\endgroup\$
    – Transistor
    Oct 29, 2022 at 11:07

2 Answers 2

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You are supposed to take square root of drain current and then plot it. Then extend the line to x-axis to get the intercept which is the threshold voltage.

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From wikipedia:

The threshold voltage, commonly abbreviated as Vth or VGS(th), of a field-effect transistor (FET) is the minimum gate-to-source voltage (VGS) that is needed to create a conducting path between the source and drain terminals.

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