Variable gain amplifier and D/A converter

A variable gain amplifier for amplifying an input voltage at a gain defined by a binary code, comprising:

• a signal input terminal that inputs the input voltage therein;
• a signal output terminal that outputs an amplified voltage therethrough;
• a charge cumulation means that accumulates a charge, and cumulatively adds a charge corresponding to the input voltage or a predetermined voltage to an accumulated charge according to a data value in each bit of the binary code;
• a charge division means that divides the charge accumulated in the charge cumulation means with a predetermined ratio, and accumulates a divided charge;
• and
• a control means that initializes the charge accumulated in the charge cumulation means, executes a charge cumulating operation by the charge cumulation means and a charge dividing operation by the charge division means according to each bit of the binary code sequentially from a least significant bit, wherein
• the charge cumulation means is provided by
• an operational amplifier having an input terminal and an output terminal coupled with the signal output terminal,
• a first capacitor connectable between the output terminal and the input terminal of the operational amplifier and having one end connectable to the signal input terminal so that the first capacitor accumulates the charge corresponding to the input voltage or the predetermined voltage, and
• a second capacitor connectable between the output terminal and the input terminal of the operational amplifier so that the second capacitor accumulates a predetermined initial charge,
• the charge division means is provided by the operational amplifier, the first capacitor and the second capacitor,
• the control means initializes the charge in the second capacitor,
• the control means executes to accumulate a predetermined change or the charge corresponding to the input voltage in the first capacitor according to a data value of each bit of the binary code sequentially from the least significant bit, and
• the control means executes a charge dividing operation and a charge adding operation with the first and second capacitors by simultaneously coupling the first and second capacitors between the output terminal and the input terminal of the operational amplifier.

A variable gain amplifier for amplifying an input voltage at a predetermined gain, comprising:

• a signal input terminal that inputs the input voltage therein;
• a signal output terminal that outputs an amplified voltage therethrough;
• an operational amplifier having a non-inverting input terminal held at a predetermined potential and output terminal connected to the signal output terminal;
• a first capacitor connectable between the output terminal and an inverting input terminal of the operational amplifier;
• a second capacitor having one end connectable at least to the output terminal of the operational amplifier and the other end connectable at least to the inverting input terminal of the operational amplifier;
• and
• a control means, wherein
• the control means executes a first process and a second process,
• the control means further executes to repeat a third process and the second process alternately according to a predetermined requirement,
• in the first process, the charge corresponding to the input voltage is accumulated at least in each of the first and second capacitors,
• in the second process, the first capacitor is connected between the output terminal and the inverting input terminal of the operational amplifier, and the other end of the second capacitor is connected to the inverting input terminal of the operational amplifier in order to transfer the charge of the second capacitor to the first capacitor,
• in the second process, connection of the first capacitor and connection of the second capacitor are executed simultaneously so that the control means executes charge adding operation, and
• in the third process, the other end of the second capacitor is disconnected to the inverting input terminal of the operational amplifier with connecting the first capacitor between the output terminal and the inverting input terminal of the operational amplifier, and the one end of the second capacitor is connected to the output terminal of the operational amplifier in order to accumulate a charge corresponding to an output voltage in the second capacitor.

A D/A converter for converting a reference voltage to an analog voltage according to a binary code and outputting the analog voltage, the converter comprising:

• a signal output terminal that outputs the analog voltage therethrough;
• a charge division means that accumulates a charge therein, divides an accumulated charge according to a predetermined ratio, and accumulates a divided charge again;
• a charge cumulation means that accumulates a charge therein, adds an accumulated charge to the charge accumulated in the charge division means, and accumulates an added charge again;
• and
• a control means, wherein
• the control means initially executes to accumulate a charge corresponding to the reference voltage in the charge division means,
• the control means initializes the charge accumulated in the charge cumulation means,
• the control means executes a charge dividing operation by the charge division means according to each bit of a binary code sequentially from a most significant bit,
• the control means executes a charge adding operation by the charge cumulation means according to a data value in each bit,
• the charge division means includes
• an operational amplifier having an input terminal and an output terminal connected to the signal output terminal,
• a first capacitor connectable between the output terminal and the input terminal of the operational amplifier so that the first capacitor accumulates the charge corresponding to the reference voltage, and
• a second capacitor connectable between the output terminal and the input terminal of the operational amplifier so that the second capacitor accumulates a predetermined charge without affecting the charge accumulated in the first capacitor,
• the control means simultaneously connects the first and second capacitors between the output terminal and the input terminal of the operational amplifier so as to execute the charge dividing operation by the charge division means,
• the charge cumulation means is provided by the operational amplifier, the first or second capacitor, and a third capacitor,
• the third capacitor connectable between the output terminal and the input terminal of the operational amplifier so that the third capacitor accumulates a predetermined initial charge, and
• the control means transfers the charge accumulated in the first or second capacitor to the third capacitor so as to execute the charge adding operation by the charge cumulation means.

A D/A converter for converting a reference voltage to an analog voltage according to a binary code and outputting the analog voltage, the converter comprising:

• a signal output terminal that outputs the analog voltage therethrough;
• a charge cumulation means that accumulates charge therein, cumulatively adds an accumulated charge to a charge corresponding to the reference voltage or a predetermined charge, which is different from the charge corresponding to the reference voltage, according to a data value in each bit of the binary code;
• a charge division means that divides the charge accumulated in the charge cumulation means according to a predetermined ratio, and accumulates a divided charge therein;
• and
• a control means, wherein
• the control means initializes the charge accumulated in the charge cumulation means,
• the control means executes a charge cumulating operation by the charge cumulation means and a charge dividing operation by the charge division means according to each bit of the binary code sequentially from a least significant bit,
• each of the charge cumulation means and charge division means includes
• an operational amplifier having an input terminal and an output terminal connected to the signal output terminal,
• a first capacitor connectable between the output terminal and the input terminal of the operational amplifier so that the first capacitor accumulates the charge corresponding to the reference voltage or the predetermined charge different from the charge corresponding to the reference voltage, and
• a second capacitor connectable between the output terminal and the input terminal of the operational amplifier so that the second capacitor accumulates a predetermined initial charge,
• the control means initializes the charge in the second capacitor,
• the control means executes to accumulate the charge corresponding to the reference voltage or the predetermined charge different from the charge corresponding to the reference voltage in the first capacitor according to an data value in each bit of the binary code sequentially from the least significant bit, and
• the control means simultaneously connects the first and second capacitors between the output terminal and the input terminal of the operational amplifier so that the control means executes an adding operation of the charges accumulated in the first and second capacitors and a dividing operation of the charges between the first and second capacitors.

A D/A converter for converting a reference voltage to an analog voltage according to a digital value and outputting the analog voltage, the converter comprising:

• a signal output terminal that outputs the analog voltage therethrough;
• an operational amplifier having a non-inverting input terminal held at a predetermined potential and an output terminal connected to the signal output terminal;
• first, second, and third capacitors, wherein one end of each capacitor is connected or connectable at least to the output terminal of the operational amplifier, and the other end of each capacitor is connected or connectable to the inverting input terminal of the operational amplifier;
• and
• a control means, wherein
• the control means executes first to fourth processes,
• in the first process, the charge corresponding to the reference voltage is accumulated in the first capacitor, and the charges in the second and third capacitors are initialized,
• in the second process, the first and second capacitors are simultaneously connected between the output terminal and the inverting input terminal of the operational amplifier in order to distribute the charge between the first and second capacitors with maintaining the charge in the third capacitor
• in the third process, the charge in the second capacitor is initialized with maintaining the charges in the first and third capacitors according to each bit of the digital value sequentially from a higher bit to a lower bit,
• in the third process, when one bit represents a first logical level, a starting point is provided by the second process,
• in the fourth process, when one bit represents a second logical level, a starting point is provided by the second process, and
• in the fourth process, the third capacitor is connected between the output terminal and the inverting input terminal of the operational amplifier in order to transfer the charge in the second capacitor to the third capacitor with maintaining the charge in the first capacitor so that the control means executes charge adding operation.

A variable gain amplifier for converting a reference voltage into an analog voltage according to a digital value, offsetting an input voltage by the analog voltage, amplifying an offset input voltage at a designated gain, and outputting an amplified voltage, the amplifier comprising:

• a signal input terminal that inputs the input voltage therein;
• a signal output terminal that outputs the amplified voltage therethrough;
• an operational amplifier having a non-inverting input terminal held at a predetermined potential and an output terminal connected to the signal output terminal;
• first, second, and third capacitors, each of which includes one end connectable or connected to at least the output terminal of the operational amplifier and the other end connectable or connected to the non-inverting input terminal of the operational amplifier;
• and
• a control means, wherein
• the control means executes first to fourth processes so that the reference voltage is converted to the analog voltage corresponding to the digital value,
• in the first process, the charge corresponding to the reference voltage is accumulated in the first capacitor, and the charges in the second and third capacitors are initialized,
• in the second process, the first and second capacitors are simultaneously connected between the output terminal and the inverting input terminal of the operational amplifier in order to distribute the charge between the first and second capacitors with maintaining the charge in the third capacitor,
• in the third process, the charge in the second capacitor is initialized with maintaining the charges in the first and third capacitors according to each bit of the digital value sequentially from a higher bit to a lower bit,
• in the third process, when one bit represents a first logical level, a starting point is provided by the second process,
• in the fourth process, when one bit represents a second logical level, a starting point is provided by the second process, and
• in the fourth process, the third capacitor is connected between the output terminal and the inverting input terminal of the operational amplifier in order to transfer the charge in the second capacitor to the third capacitor with maintaining the charge in the first capacitor so that the control means executes charge adding operation,
• the control means further executes a fifth process and a sixth process, and furthermore, executes to repeat a seventh process and the sixth process alternately, or to repeat an eighth process and the sixth process alternately according to a predetermined requirement, so that the offset input voltage is amplified at the designated gain,
• in the fifth process, a charge corresponding to a difference between the input voltage and the analog voltage is accumulated in the first and second capacitors,
• in the sixth process, the first and third capacitors are connected between the output terminal and an inverting input terminal of the operational amplifier in order to distribute the charge between the first and third capacitors with maintaining the charge in the second capacitor,
• in the seventh process, the third capacitor is switched to a predetermined charge state with maintaining the charges in the first and second capacitors, and
• in the eighth process, the second capacitor is connected between the output terminal and the inverting input terminal of the operational amplifier in order to transfer the charge in the third capacitor to the second capacitor with maintaining the charge in the first capacitor.