Dear All,
when looking at an I-V curve, what does it say about the device if the saturation region occures in the positive Vgs region or in the negative Vgs region?
Best Regards,
Dear Sara,
when the saturation region occurs in the positive VGS region , this means that the device is an enhancement type and when the saturation occurs in the negative VGS region it means that the FET is a depletion type. However, in the first case the cut off must be in a less positive voltage and in the second case the cut off voltage must be in a a more negative VGS voltage. In both cases VDS must be positive.
This is an n-channel fet.
Sara, if you show us your curves we can give more precise comments on them. Other wise yiou have to precise your question according to this comment.
Best wishes
Dear Sara,
For Enhancement N-channel FET, the saturation occurs in the positive VGS.
For Depletion N-channel FET, the saturation occurs in the negative VGS.
For Enhancement P-channel FET, the saturation occurs in the negative VGS.
For Depletion P-channel FET, the saturation occurs in the positive VGS.
Noted that the IDS in N-channel FET is positive and negative in P-channel FET.
thank you all, as requested i attached a figure of the device I-V curves, the shifted curve is due to the UV exposure. it can be seen that due to the shift the saturation region moves to the positive Vgs.
does this mean that the device converts from enhancement to depletion mode?
Dear Sara,
welcome,
Your transistor is a p-channel transistor having negative VDS, negative VGS and negative ID assuming that ID is measured inward of the drain terminal.
It is clear that this transistor will normally saturate in the more negative VGS values when it is in dark or illuminated. The illumination causes the saturation region to shift to more positive VGS. Since there will be an additional photo current added to the field effect current.
Best wishes
According to the figure, it is depletion n-channel.
If the Vds applied is negative, it is Enhancement P-channel FET
Ismail
so it is Enhacement P channel FET.
VDS=-50 V , is it TFT or Organic thin film transistor OTFT?
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