[amp_mcq option1=”TRUE” option2=”nan” option3=”nan” option4=”nan” correct=”option1″]
The correct answer is False. The substrate bias voltage is negative for nMOS.
The substrate bias voltage is the voltage applied to the substrate of a MOSFET. The substrate is the semiconductor material that forms the body of the MOSFET. The substrate bias voltage is typically applied to create a reverse bias junction between the substrate and the source and drain regions of the MOSFET. This reverse bias junction helps to prevent leakage current and improve the performance of the MOSFET.
In an nMOS transistor, the source and drain regions are made of n-type semiconductor material, while the substrate is made of p-type semiconductor material. When a positive voltage is applied to the source and drain regions, the electrons in the n-type regions are attracted to the positive voltage and flow towards the drain region. This creates a current flow through the transistor.
However, if a positive voltage is also applied to the substrate, the electrons in the p-type substrate will be attracted to the positive voltage and flow towards the source region. This will create a current flow in the opposite direction to the current flow through the transistor. This is called a parasitic current flow and it can reduce the performance of the transistor.
To prevent parasitic current flow, the substrate bias voltage is typically applied to a negative voltage. This reverse bias voltage creates a depletion region at the junction between the substrate and the source and drain regions. This depletion region prevents the electrons in the p-type substrate from flowing towards the source region.
In conclusion, the substrate bias voltage is negative for nMOS transistors. This is done to prevent parasitic current flow and improve the performance of the transistor.