In inverter circuits, depletion mode transistors are used as the load.

Depletion mode transistors are a type of field-effect transistor (FET) in which the channel is already formed without any external voltage applied. These transistors have a channel that is "depleted" of majority charge carriers (either electrons or holes) when no voltage is applied between the gate and the source. When a negative voltage is applied to the gate with respect to the source, the channel opens up and allows current to flow through.

Explanation:
Depletion mode transistors have some characteristics that make them suitable for use as the load in inverter circuits:

1. Voltage levels: Depletion mode transistors can operate with both positive and negative voltage levels. This is important for inverter circuits, as they need to handle both high and low voltage levels.

2. Current flow: Depletion mode transistors allow current to flow even when the gate-to-source voltage is zero or negative. This means that they can conduct current in the absence of an input signal, which is essential for the proper operation of an inverter circuit.

3. Switching speed: Depletion mode transistors have a fast switching speed, which means they can quickly turn on and off in response to changes in the input signal. This is important for inverter circuits, as they need to convert a DC input signal into an AC output signal.

4. Design simplicity: Depletion mode transistors do not require an additional biasing circuit to operate. This simplifies the design of the inverter circuit and reduces the number of components required.

Overall, the use of depletion mode transistors as loads in inverter circuits allows for efficient and reliable operation, with fast switching speeds and the ability to handle both positive and negative voltage levels.