Semiconductor output circuit
View Patent ↗To improve a depletion transistor provided between a control terminal of an output transistor and an output terminal coupled to a load not to enter a conductive state when the output transistor is in the conductive state. The output transistor is served as a source follower. Control voltages which controlling the conductive state/nonconductive state of the depletion transistor are supplied to both a control terminal (gate) and a substrate terminal (back gate) of the depletion transistor.
1. A semiconductor output circuit, comprising:
an output transistor coupled between a power supply line and an output terminal being configured to be coupled with a load;
a depletion transistor coupled between a control terminal of the output transistor and the output terminal; and
a control circuit supplying control voltages to both a control terminal and a substrate terminal of the depletion transistor, a conductive state/nonconductive state of the depletion transistor being controlled by the control voltages.
2. A semiconductor output circuit according to claim 1 , further comprising:
a constant current source device coupled in series with the depletion transistor between the control terminal of the output transistor and the output terminal.
3. A semiconductor output circuit according to claim 2 , wherein the constant current source device comprises a depletion transistor.
4. A semiconductor output circuit according to claim 1 , further comprising:
a gate drive circuit,
wherein the output transistor is driven by an output of the gate drive circuit, and the output of the gate drive circuit becomes a high impedance state when the output transistor is caused to enter the nonconductive state.
5. A semiconductor output circuit according to claim 4 , wherein the gate drive circuit, in response to a control signal causing the output transistor to enter the conductive state, generates a higher potential than a potential of the power supply line to drive the output transistor with the higher potential.