Granted Patent B2

US 8,649,477 · App. 13/717,855 · Granted Feb 11, 2014

Abstract

Claims (46)

1. A level shifter comprising:

an input terminal to which an input voltage is applied;

a first capacitor;

a first transistor having a source electrode and a drain electrode that are provided between the input terminal and one of electrodes of the first capacitor, and a gate electrode connected to the other of the electrodes of the first capacitor;

a second transistor having a source electrode and a drain electrode that are provided between the input terminal and the other electrode of the first capacitor;

a signal generating unit configured to generate a signal for switching the second transistor between conduction and non-conduction and supply the signal to the gate electrode of the second transistor; and

an output terminal for outputting, in a period when the input voltage is provided to the input terminal, a voltage at the other electrode of the first capacitor which is level-shifted as an output voltage,

wherein the signal generating unit further includes:

a control terminal to which a control signal for generating the output voltage is applied;

a reset terminal to which a reset signal for resetting a circuit state is applied;

a second capacitor connected between the ate electrode of the second transistor and the one electrode of the first capacitor;

a third transistor having a gate electrode connected to the reset terminal, one of a source electrode and a drain electrode connected to the control terminal, and the other of the source electrode and the drain electrode connected to the ate electrode of the second transistor;

a fourth transistor having a gate electrode connected to the one electrode of the first capacitor, one of a source electrode and a drain electrode connected to the gate electrode of the second transistor, and the other of the source electrode and the drain electrode connected to a reference terminal; and

a fifth transistor having a gate electrode connected to the reset terminal, one of a source electrode and a drain electrode connected to the one electrode of the first capacitor, and the other of the source electrode and the drain electrode connected to the reference terminal.

2. The level shifter according to claim 1 ,

wherein a voltage corresponding to the input voltage is charged in the first capacitor in a period when the input voltage is provided to the input terminal and when the second transistor is in a conducting state by the signal generating unit, and the input voltage is applied to the one electrode of the first capacitor through the first transistor set to be in a conducting state by an application of the input voltage to the gate electrode, and

the output voltage having a voltage amplitude greater than the input voltage is generated in the other electrode of the first capacitor by the signal generating unit setting the second transistor in a non-conducting state in response to the application of the input voltage to the one electrode of the first capacitor, and the output voltage is provided from the output terminal.

3. The level shifter according to claim 1 , wherein the first to fifth transistors are n-type thin-film transistors.

4. The level shifter according to claim 1 , wherein the first to fifth transistors are p-type thin-film transistors.

5. An inverter circuit comprising:

a logic inverting unit configured to invert a logic of an input signal; and

the level shifter according to claim 1 which inputs an output signal from the logic inverting unit to the input terminal, shifts a level of the input voltage, and outputs the level-shifted input voltage.

6. An inverter circuit comprising:

the level shifter according to claim 1 ;

an inverter input terminal to which two types of input voltages representing logic states are provided;

an inverter output terminal which outputs an output voltage representing one of logic states obtained by inverting the logic states represented by the two types of the input voltages;

a first reference line for supplying a first reference voltage representing one of the logic states;

a second reference line for supplying a second reference voltage representing the other of the logic states;

a first input transistor having (i) a gate electrode and (ii) one of a source electrode and a drain electrode that are connected to the first reference line, and the other of the source electrode and the drain electrode connected to the input terminal of the level shifter;

a second input transistor having a gate electrode connected to the inverter input terminal, one of a source electrode and a drain electrode connected to the input terminal, and the other of the source electrode and the drain electrode connected to the second reference line;

a first output transistor having a gate electrode connected to the output terminal of the level shifter, one of a source electrode and a drain electrode connected to the first reference line, and the other of the source electrode and the drain electrode connected to the inverter output terminal; and

a second output transistor having a gate electrode connected to the inverter input terminal, one of a source electrode and a drain electrode connected to the inverter output terminal, and the other of the source electrode and the drain electrode connected to the second reference line,

wherein the inverter input terminal is further connected to the reset terminal of the level shifter, and

the first reference line is further connected to the control terminal of the level shifter.

7. A shift register having unit circuits connected in multiple stages and which receives a clock signal and an input signal, and outputs an output signal obtained by shifting the input signal for a predetermined delay time, the shift register comprising

the level shifter according to claim 1 which shifts a level of a clock amplitude of the clock signal as the input voltage, and outputs the level-shifted clock amplitude to at least one of the unit circuits as the output voltage.

8. A level shifter comprising:

an input terminal to which an input voltage is applied;

a first capacitor;

a first transistor having a source electrode and a drain electrode that are provided between the input terminal and one of electrodes of the first capacitor, and a gate electrode connected to the other of the electrodes of the first capacitor;

a second transistor having a source electrode and a drain electrode that are provided between the input terminal and the other electrode of the first capacitor;

a signal generating unit configured to generate a signal for switching the second transistor between conduction and non-conduction and supply the signal to the gate electrode of the second transistor; and

an output terminal for outputting, in a period when the input voltage is provided to the input terminal, a voltage at the other electrode of the first capacitor which is level-shifted as an output voltage,

wherein the first transistor and the second transistor have depletion characteristics,

a voltage corresponding to the input voltage is charged in the first capacitor in a period when the input voltage is provided to the input terminal and when the second transistor is in a conducting state by the signal generating unit, and the input voltage is applied to the one electrode of the first capacitor through the first transistor set to be in a conducting state by an application of the input voltage to the gate electrode, and

the output voltage having a voltage amplitude greater than the input voltage is generated in the other electrode of the first capacitor by the signal generating unit setting the second transistor in a non-conducting state in response to the application of the input voltage to the one electrode of the first capacitor, and the output voltage is provided from the output terminal.

Assignments (6)