OPERATIONAL AMPLIFIER AND LIQUID CRYSTAL DRIVE DEVICE USING SAME, AS WELL AS PARAMETER SETTING CIRCUIT, SEMICONDUCTOR DEVICE, AND POWER SUPPLY UNIT

• US 20110128277A1
• Filed: 11/22/2010
• Published: 06/02/2011
• Est. Priority Date: 11/27/2009
• Status: Active Grant

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Murakami, Kazuhiro
• Granted Patent: US 8,754,881 B2
• Time in Patent Office: Days
• US Class Current: 345/212
• CPC Class Codes: G09G 3/3655 Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors
• CPC Class Codes: G09G 3/3677 suitable for active matrices only
• CPC Class Codes: G09G 3/3688 suitable for active matrices only
• CPC Class Codes: H03F 2203/45692 the LC comprising one or more resistors in series with a capacitor coupled to the LC by feedback
• CPC Class Codes: H03F 3/3022 CMOS common source output SEPP amplifiers H03F3/3008 takes precedence
• CPC Class Codes: H03F 3/45183 Long tailed pairs H03F3/4521, H03F3/45237 take precedence

Abstract

The operational amplifier according to the present invention has at least one differential input part for generating a voltage signal corresponding to an electric potential difference between a positive-phase input signal and a negative-phase input signal by using a differential pair configured from a pair of transistors; an output part for generating and outputting an output signal of a logic level corresponding to the voltage signal generated by the differential input part; at least one auxiliary current generator for detecting a sudden change in the positive-phase input signal or the negative-phase input signal and generating an auxiliary current; and a drive current generator for adding together a predetermined reference current and the auxiliary current and generating a drive current of the differential input part.

Claims

1. An operational amplifier comprising:

at least one differential input part for generating a voltage signal corresponding to an electric potential difference between a positive-phase input signal and a negative-phase input signal by using a differential pair configured from a pair of transistors;

an output part for generating and outputting an output signal of a logic level corresponding to the voltage signal generated by the differential input part;

at least one auxiliary current generator for detecting a sudden change in the positive-phase input signal or the negative-phase input signal and generating an auxiliary current; and

a drive current generator for adding together a predetermined reference current and the auxiliary current and generating a drive current of the differential input part.

2. The operational amplifier of claim 1, wherein the auxiliary current generator comprises:

a differentiating circuit for receiving an input of a voltage that appears in a common connection end of the differential pair, and generating a differential waveform signal thereof; and

a switch for controlling generation or non-generation of the auxiliary current in accordance with the differential waveform signal.

3. The operational amplifier of claim 2, wherein the differentiating circuit is a CR filter having a resistor and a capacitor.

4. The operational amplifier of claim 1, wherein the differential input part comprises:

a first differential input part having a first differential pair comprising a pair of p-channel MOS field effect transistors; and

a second differential input part having a second differential pair comprising a pair of n-channel MOS field effect transistors.

5. The operational amplifier of claim 4, wherein the auxiliary current generator comprises:

a first auxiliary current generator for monitoring a first voltage that appears in a common connection end of the first differential pair, detecting a fall from a high level to a low level in the positive-phase input signal, and generating a first auxiliary current; and

a second auxiliary current generator for monitoring a second voltage that appears in a common connection end of the second differential pair, detecting a rise from a low level to a high level in the positive-phase input signal, and generating a second auxiliary current.

6. A liquid crystal drive device comprising a unit gain amplifier provided in a signal path to a liquid crystal panel, wherein the unit gain amplifier comprises:

at least one differential input part for generating a voltage signal corresponding to an electric potential difference between a positive-phase input signal and a negative-phase input signal by using a differential pair configured from a pair of transistors;

an output part for generating and outputting an output signal of a logic level corresponding to the voltage signal generated by the differential input part;

at least one auxiliary current generator for detecting a sudden change in the positive-phase input signal or the negative-phase input signal and generating an auxiliary current; and

a drive current generator for adding together a predetermined reference current and the auxiliary current and generating a drive current of the differential input part.

7. A parameter setting circuit integrated in a semiconductor device and comprising:

a first external terminal impressed with a fixed voltage, and a second external terminal connected to the first external terminal via an external resistor; and

passing a current through the external resistor by impressing a predetermined reference voltage between the first external terminal and the second external terminal, and setting an internal parameter for the semiconductor device in accordance with the current.

8. The parameter setting circuit of claim 7, comprising:

a transistor having one end connected to the second external terminal;

a resistor having one end connected to another end of the transistor; and

an operational amplifier having a first input end connected to the first external terminal via a voltage source for generating the reference voltage, having a second input end connected to the second external terminal, and having an output end connected to a control end of the transistor;

wherein the parameter setting circuit outputs a voltage signal brought out from one end of the resistor as the internal parameter.

9. The parameter setting circuit of claim 8, wherein the second external terminal is an input terminal, an output terminal, or an input/output terminal for a logic signal.

10. The parameter setting circuit of claim 9, wherein the logic signal is an enable signal for controlling the operation or non-operation of the semiconductor device.

11. A semiconductor device comprising:

a first external terminal impressed with a fixed voltage;

a second external terminal connected to the first external terminal via an external resistor;

an overcurrent protection circuit for comparing a predetermined threshold voltage and a detected voltage whose voltage value varies in accordance with a magnitude of a monitored current, and generating an overcurrent protection signal; and

a parameter setting circuit for outputting the threshold voltage;

wherein the parameter setting circuit passes a current through the external resistor by impressing a predetermined reference voltage between the first external terminal and the second external terminal, and sets the threshold voltage in accordance with the current.

12. The semiconductor device according to claim 11, comprising a switch drive circuit provided with a shut-down function based on the overcurrent protection signal.

13. A power supply unit comprising:

a semiconductor device; and

a switching element for generating a desired output voltage from an input voltage due to performance of on/off control by the semiconductor device;

wherein the semiconductor device has the following components;

a first external terminal impressed with a fixed voltage;

a second external terminal connected to the first external terminal via an external resistor;

an overcurrent protection circuit for comparing a predetermined threshold voltage and a detected voltage whose voltage value varies in accordance with a magnitude of a monitored current, and generating an overcurrent protection signal;

a switch drive circuit provided with a shut-down function based on the overcurrent protection signal; and

a parameter setting circuit for outputting the threshold voltage; and

wherein the parameter setting circuit passes a current through the external resistor by impressing a predetermined reference voltage between the first external terminal and the second external terminal, and sets the threshold voltage in accordance with the current.

14. A liquid crystal drive device comprising:

a unit gain amplifier provided in a signal path to a liquid crystal display panel; and

a power supply circuit for generating a desired output voltage from an input voltage and supplying electrical power to the unit gain amplifier;

wherein the unit gain amplifier has the following components;

at least one differential input part for generating a voltage signal corresponding to an electric potential difference between a positive-phase input signal and a negative-phase input signal by using a differential pair configured from a pair of transistors;

an output part for generating and outputting an output signal of a logic level corresponding to the voltage signal generated by the differential input part;

at least one auxiliary current generator for detecting a sudden change in the positive-phase input signal or the negative-phase input signal and generating an auxiliary current; and

a drive current generator for adding together a predetermined reference current and the auxiliary current and generating a drive current of the differential input part;

wherein the semiconductor device comprises;

a first external terminal impressed with a fixed voltage; and

a second external terminal connected to the first external terminal via an external resistor; and

wherein the power supply circuit comprises;

an overcurrent protection circuit for generating an overcurrent protection signal showing whether a monitored current is in an overcurrent state; and

an overcurrent protection value setting circuit for passing a current through the external resistor by impressing a predetermined reference voltage between the first external terminal and the second external terminal, and setting an overcurrent protection value for the overcurrent protection circuit in accordance with the current.

15. The liquid crystal drive device of claim 14, wherein the auxiliary current generator comprises:

a differentiating circuit for receiving an input of a voltage that appears in a common connection end of the differential pair and generating a differential waveform signal thereof; and

a switch for controlling generation or non-generation of the auxiliary current in accordance with the differential waveform signal.

16. The liquid crystal drive device of claim 15, wherein the differential circuit is a CR filter having a resistor and a capacitor.

17. The liquid crystal drive device of claim 14, wherein the differential input part comprises:

a first differential input part having a first differential pair configured from a pair of p-channel MOS field effect transistors; and

a second differential input part having a second differential pair configured from a pair of n-channel MOS field effect transistors.

18. The liquid crystal drive device of claim 17, wherein the auxiliary current generator comprises:

a first auxiliary current generator for monitoring a first voltage that appears in a common connection end of the first differential pair, detecting a fall from a high level to a low level in the positive-phase input signal, and generating a first auxiliary current; and

a second auxiliary current generator for monitoring a second voltage that appears in a common connection end of the second differential pair, detecting a rise from a low level to a high level in the positive-phase input signal, and generating a second auxiliary current.

19. The liquid crystal drive device of claim 17, wherein the overcurrent protection value setting circuit comprises:

a transistor having one end connected to the second external terminal;

a resistor having one end connected to another end of the transistor; and

an operational amplifier having a first input end connected to the first external terminal via a voltage source for generating the reference voltage, having a second input end connected to the second external terminal, and having an output end connected to a control end of the transistor;

wherein the overcurrent protection value setting circuit outputs a voltage signal brought out from one end of the resistor as the overcurrent protection value.

20. The liquid crystal drive device of claim 14, wherein the second external terminal is an input terminal, output terminal, or input/output terminal of a logic signal.

21. The liquid crystal drive device of claim 20, wherein the logic signal is an enable signal for controlling the operation or non-operation of the semiconductor device.

22. The liquid crystal drive device of claim 14, wherein the power supply circuit has a switch drive circuit provided with a shut-down function based on the overcurrent protection signal.

23. The liquid crystal drive device of claim 22, comprising a switching element subjected to on/off control by the switch drive circuit.