Advantages and disadvantages of depletion MOSFET?

Answer 1

Since the logic operations of depletion MOSFET is the opposite to the enhancement MOSFET, the depletion MOSFET produces positive logic circuits, such as, buffer, AND, and OR. The most significant advantage of the positive logic circuits is that it can produce positive feedback easily so that a single depletion MOSFET can become a memory cell. In contrast, you will need at least two enhancement MOSFET transistor to produce the positive feedback to build a memory cell.

The other advantages of depletion MOSFET are that it is free from sub-threshold leakage current and gate-oxide leakage current.

Since there is always a potential difference of Vdd between the gate terminal and channel for an enhancement MOSFET to cause the gate-oxide leakage current, the gate oxide leakage current is unavoidable when the transistor shrinks in size and oxide layer becomes thinner. The depletion MOSFET does not have this problem because there is no potential difference between the gate and channel.

As a enhancement MOSFET shrinking in size, there is no way to stop the subthreshold leakage current diffused across from source to drain because the drain and source terminals are closer physically. This is not a problem for depletion MOSFET because a pinched channel will stop the diffusion current completely.

The depletion MOSFET is the ideal, perfect transistor. The only disadvantage of depletion MOSFET is its inability to produce negative logic operations.