Contents
What is the effect of channel length modulation in MOSFET?
The result of CLM is an increase in current with drain bias and a reduction of output resistance. It is one of several short-channel effects in MOSFET scaling. It also causes distortion in JFET amplifiers. To understand the effect, first the notion of pinch-off of the channel is introduced.
How threshold voltage depends on channel length?
Though for long channel MOSFET, it is seen that threshold voltage is independent of device length, in reality, it can be shown that the threshold voltage is a strong function of the channel length and it actually decreases with the decrease in channel length.
When threshold voltage is more leakage current will be?
When the threshold voltage is more, leakage current will be? Explanation: Increasing the threshold voltage, leads to small leakage current when turned off and reduces current flow when turned on.
How does channel length modulation occur in a MOSFET?
Channel length modulation occurs in all field effect transistors, not just MOSFETs . To understand the effect, first the notion of pinch-off of the channel is introduced. The channel is formed by attraction of carriers to the gate, and the current drawn through the channel is nearly a constant independent of drain voltage in saturation mode.
How does channel length modulation affect drain current?
Thus, channel-length modulation means that the saturation-region drain current will increase slightly as the drain-to-source voltage increases. So we need to modify the saturation-region drain-current expression to account for channel-length modulation.
When to use a modified drain current expression?
This modified drain-current expression is a first-order approximation that is reasonably accurate for FETs with channel length greater than, say, 2 µm. As the channel length decreases, so-called “short-channel effects” become more influential, and thus the above expression (which does not account for short-channel effects) becomes less valid.
How does the length of a channel affect the current?
Because resistance is proportional to length, shortening the channel decreases its resistance, causing an increase in current with increase in drain bias for a MOSFET operating in saturation. The effect is more pronounced the shorter the source-to-drain separation, the deeper the drain junction, and the thicker the oxide insulator.