ANALOG SWITCH

• US 20090108911A1
• Filed: 10/30/2008
• Published: 04/30/2009
• Est. Priority Date: 10/30/2007
• Status: Abandoned Application

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Nakahara, Hironori, Horiuchi, Sachito
• Application Number:
  US12/261,167
• Publication Number:
  US 20090108911A1
• Time in Patent Office: Days
• US Class Current: 327/434
• CPC Class Codes: H03K 17/063 in field-effect transistor switches

Abstract

An analog signal is input to an input terminal. An analog signal is output via an output terminal. A first transistor is an N-channel MOSFET, and is provided between the input terminal and the output terminal. A first resistor is provided between the gate of the first transistor and a first fixed voltage terminal (power supply terminal), which sets the gate of the first transistor to a high-impedance state.

Claims

1. An analog switch comprising:

an input terminal via which an analog signal is input;

an output terminal via which the analog signal is output;

a first N-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor) provided between the input terminal and the output terminal; and

a first resistor provided between the gate of the first MOSFET and a first fixed voltage terminal.

2. An analog switch according to claim 1, wherein the analog signal is a signal that swings between a negative voltage and a positive voltage with the ground voltage as the midpoint,

and wherein, in the ON state of the analog switch, the power supply voltage is applied to the first fixed voltage terminal.

3. An analog switch according to claim 1, further including a second N-channel MOSFET which is connected in series with the first MOSFET between the input terminal and the output terminal, such that the gate thereof is connected to the gate of the first MOSFET so as to form a common gate.

4. An analog switch according to claim 1, wherein the analog signal is an audio signal,

and wherein a bypass filter configured of the first resistor and the gate-source capacitance of the first MOSFET allows a signal in the audio frequency band to pass through.

5. An analog switch according to claim 1, further including a first capacitor in the form of a MIM (Metal Insulator Metal) capacitance between the input terminal and the gate of the first MOSFET.

6. An analog switch according to claim 1, further including a second capacitor in the form of a MIM capacitance between the output terminal and the gate of the first MOSFET.

7. An analog switch according to claim 3, further including a third MOSFET provided between the first fixed voltage terminal and the first resistor, such that the gate voltage is controlled according to the ON/OFF operation of the analog switch.

8. An analog switch according to claim 3, further including a fourth MOSFET provided between the node that connects the first MOSFET and the second MOSFET and the first resistor, such that the gate voltage thereof is controlled according to the ON/OFF operation of the analog switch.

9. An analog switch according to claim 3, further including a fifth MOSFET provided between the node that connects the first MOSFET and the second MOSFET and the ground terminal, such that the gate voltage thereof is controlled according to the ON/OFF operation of the analog switch.

10. An analog switch according to claim 1, further including a first diode in series with the first resistor between the gate of the first MOSFET and the first fixed voltage terminal, such that the cathode thereof is arranged on the gate side of the first MOSFET.

11. An analog switch according to claim 1, further including:

a sixth MOSFET which is a P-channel MOSFET provided between the input terminal and the output terminal; and

a second resistor provided between the gate of the sixth MOSFET and the second fixed voltage terminal.

15. An analog switch according to claim 1, wherein the analog signal is an audio signal,

and wherein an electroacoustic transducing device is connected to the output terminal as a load.

16. A selector circuit including a plurality of analog switches according to claim 1,

wherein the output terminals of the plurality of analog switches are connected so as to form a common output terminal.

17. A selector circuit including a plurality of analog switches according to claim 1,

wherein the input terminals of the plurality of analog switches are connected so as to form a common input terminal.

12. An analog switch comprising:

an input terminal via which an analog signal is input;

an output terminal via which the analog signal is output;

a sixth P-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor) provided between the input terminal and the output terminal; and

a second resistor provided between the gate of the sixth MOSFET and a second fixed voltage terminal.

13. An analog switch according to claim 12, wherein the analog signal is a signal that swings between a negative voltage and a positive voltage with the ground voltage as the midpoint,

and wherein, in the ON state of the analog switch, the ground voltage is applied to the second fixed voltage terminal.

14. An analog switch according to claim 12, further including a seventh P-channel MOSFET which is connected in series with the sixth MOSFET between the input terminal and the output terminal, such that the gate thereof is connected to the gate of the sixth MOSFET so as to form a common gate.

18. An analog switch comprising:

an input terminal via which an analog switch is input;

an output terminal via which the analog signal is output;

a first N-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor) provided between the input terminal and the output terminal; and

a first diode provided between the gate of the first MOSFET and a first fixed voltage terminal, such that the cathode thereof is arranged on the gate side of the first MOSFET.

19. An analog switch according to claim 18, wherein the analog signal is a signal that swings between a negative voltage and a positive voltage with the ground voltage as the midpoint,

and wherein, in the ON state of the analog switch, the power supply voltage is applied to the first fixed voltage terminal.

20. An analog switch according to claim 18, further including a second N-channel MOSFET which is connected in series with the first MOSFET between the input terminal and the output terminal, such that the gate thereof is connected to the gate of the first MOSFET so as to form a common gate.

21. An analog switch according to claim 18, further including a first capacitor in the form of a MIM (Metal Insulator Metal) capacitance between the input terminal and the gate of the first MOSFET.

22. An analog switch according to claim 18, further including a second capacitor in the form of a MIM capacitance between the output terminal and the gate of the first MOSFET.

23. An analog switch according to claim 20, further including a third MOSFET provided between the first fixed voltage terminal and the anode of the first diode, such that the gate voltage is controlled according to the ON/OFF operation of the analog switch.

24. An analog switch according to claim 20, further including a fourth MOSFET provided between the node that connects the first MOSFET and the second MOSFET and the cathode of the first diode, such that the gate voltage thereof is controlled according to the ON/OFF operation of the analog switch.

25. An analog switch according to claim 20, further including a fifth MOSFET provided between the node that connects the first MOSFET and the second MOSFET and the ground terminal, such that the gate voltage thereof is controlled according to the ON/OFF operation of the analog switch.

26. An analog switch according to claim 18, further including a first resistor provided in series with the first diode between the gate of the first MOSFET and the first fixed voltage terminal.

27. An analog switch according to claim 18, further including:

a sixth MOSFET which is a P-channel MOSFET provided between the input terminal and the output terminal; and

a second diode provided between the gate of the sixth MOSFET and a second fixed voltage terminal, such that the anode thereof is arranged on the gate side of the sixth MOSFET.

32. An analog switch according to claim 18, wherein the analog signal is an audio signal,

and wherein an electroacoustic transducing device is connected to the output terminal as a load.

33. A selector circuit including a plurality of analog switches according to claim 18,

wherein the output terminals of the plurality of analog switches are connected so as to form a common output terminal.

34. A selector circuit including a plurality of analog switches according to claim 18,

wherein the input terminals of the plurality of analog switches are connected so as to form a common input terminal.

28. An analog switch comprising:

an input terminal via which an analog signal is input;

an output terminal via which the analog signal is output;

a sixth MOSFET (Metal Oxide Semiconductor Field Effect Transistor) which is a P-channel MOSFET provided between the input terminal and the output terminal; and

a second diode provided between the gate of the sixth MOSFET and a second fixed voltage terminal, in the direction in which the anode thereof is arranged on the gate side of the sixth MOSFET.

29. An analog switch according to claim 28, wherein the analog signal is a signal that swings between a negative voltage and a positive voltage with the ground voltage as the midpoint,

and wherein, in the ON state of the analog switch, the ground voltage is applied to the second fixed voltage terminal.

30. An analog switch according to claim 28, further including a seventh P-channel MOSFET which is connected in series with the sixth MOSFET between the input terminal and the output terminal, such that the gate thereof is connected to the gate of the sixth MOSFET so as to form a common gate.

31. An analog switch comprising:

an input terminal via which an analog signal is input;

an output terminal via which the analog signal is output;

a first MOSFET (Metal Oxide Semiconductor Field Effect Transistor) provided between the input terminal and the output terminal; and

an impedance element which is provided between the gate of the first MOSFET and a first fixed voltage terminal, and which charges/discharges the gate of the first MOSFET according to the voltage of the analog signal.