Introduction:
Depletion mode n-MOS and enhancement mode n-MOS are commonly used as active loads in integrated circuits. Both types of MOS transistors have their own advantages and disadvantages. However, when it comes to certain criteria such as sharp VTC transition, better noise margins, single power supply, and smaller overall layout area, the depletion mode n-MOS is considered better than the enhancement mode n-MOS.

Sharp VTC transition:
The VTC (Voltage Transfer Characteristic) of a transistor describes how the output voltage varies with the input voltage. In the case of depletion mode n-MOS as an active load, the VTC transition is sharper compared to the enhancement mode n-MOS. This is because the depletion mode n-MOS has a steeper sub-threshold slope, resulting in a more abrupt change in output voltage for a given change in input voltage. This sharp transition is desirable in various applications, such as in digital logic circuits, where a clear distinction between logic levels is required.

Better noise margins:
Noise margins refer to the ability of a circuit to tolerate noise without causing errors or incorrect operation. The depletion mode n-MOS as an active load provides better noise margins compared to the enhancement mode n-MOS. This is because the depletion mode n-MOS has a higher output impedance, which helps in reducing the sensitivity to noise. The higher output impedance prevents the noise from affecting the circuit operation and improves the overall noise immunity.

Single power supply:
In integrated circuits, it is often desirable to operate with a single power supply to simplify the circuit design and reduce the overall complexity. The depletion mode n-MOS as an active load is more suitable for single power supply operation compared to the enhancement mode n-MOS. This is because the depletion mode n-MOS can operate in the saturation region with a positive gate-source voltage (VGS) and does not require a negative voltage supply. In contrast, the enhancement mode n-MOS requires a negative voltage supply to operate in the saturation region, which adds complexity to the circuit design.

Smaller overall layout area:
The depletion mode n-MOS as an active load requires fewer transistors compared to the enhancement mode n-MOS, resulting in a smaller overall layout area. This is advantageous in integrated circuit design where the goal is to minimize the chip size and maximize the number of components that can be integrated onto a single chip. The smaller layout area also helps in reducing the manufacturing cost and improving the overall performance of the circuit.

Conclusion:
In conclusion, the depletion mode n-MOS as an active load is better than the enhancement mode n-MOS in terms of sharp VTC transition, better noise margins, single power supply operation, and smaller overall layout area. These advantages make the depletion mode n-MOS more suitable for various applications, especially in digital integrated circuits where high performance and compact design are essential.