Digital-to-analog converter and sensor-characteristic adjustment circuit

A digital-to-analog converter comprising:

• an R-2R resistive ladder network having resistors coupled in a ladder form in correspondence with a number of bits of a digital input signal, the R-2R resistive ladder network having an output terminal;
• a positive and a and negative dc-power-supply terminal both coupled connected to the R-2R resistive ladder network and the terminals subjected to first and second predetermined voltage references respectively, the first and second predetermined voltage references being different from each other;
• means for controlling currents flowing between the R-2R resistive ladder network and one of the positive and negative dc-power-supply terminals in response to the bits of the digital input signal to generate an analog voltage signal at the output terminal of the R-2R resistive ladder network on the basis of the first and second predetermined voltage references, the analog voltage signal depending on the digital input signal;
• a series combination of a first resistor and a second resistor located outside the R-2R resistive ladder network, the series combination being coupled between the positive and negative dc-power-supply terminals to receive the first and second predetermined voltage references;
• a third resistor located outside the R-2R resistive ladder network and coupled between the output terminal of the R-2R resistive ladder network and a junction between the first and second resistors located outside the R-2R resistive ladder network;
• and
• a conversion output terminal coupled to the junction between the first and second resistors located outside the R-2R resistive ladder network.

A digital-to-analog converter comprising:

• an R-2R resistive ladder network having resistors connected in a ladder form in correspondence with a number of bits of a digital input signal, the R-2R resistive ladder network having an output terminal;
• a positive and a negative dc-power-supply terminal both coupled to the R-2R resistive ladder network and the terminals subjected to first and second predetermined voltage references respectively, the first and second predetermined voltage references being different from each other;
• means for controlling currents flowing between the R-2R resistive ladder network and one of the positive and negative dc-power-supply terminals in response to the bits of the digital input signal to generate an analog voltage signal at the output terminal of the R-2R resistive ladder network on the basis of the first and second predetermined voltage references, the analog voltage signal depending on the digital input signal;
• a series combination of a first resistor, a second resistor, and a third resistor located outside the R-2R resistive ladder network, the series combination being coupled between the positive and negative dc-power-supply terminals to receive the first and second predetermined voltage references, wherein a junction between the first and second resistors located outside the R-2R resistive ladder network is coupled to the output terminal of the R-2R resistive ladder network;
• and
• a conversion output terminal coupled to a junction between the second and third resistors located outside the R-2R resistive ladder network.

A circuit for adjusting characteristics of a sensor, comprising:

• a digital-to-analog converter converting a digital reference signal into an analog reference signal;
• and
• means for adjusting an output signal of the sensor in response to the analog reference signal generated by the digital-to-analog converter;
• wherein the digital-to-analog converter comprises:
• an R-2R resistive ladder network having resistors coupled in a ladder form in correspondence with a number of bits of the digital reference signal, the R-2R resistive ladder network having an output terminal;
• a positive and a negative dc-power-supply terminal both coupled to the R-2R resistive ladder network and the terminals subjected to first and second predetermined voltage references respectively, the first and second predetermined voltage references being different from each other;
• means for controlling currents flowing between the R-2R resistive ladder network and one of the positive and negative dc-power-supply terminals in response to the bits of the digital reference signal to generate an analog voltage signal at the output terminal of the R-2R resistive ladder network on the basis of the first and second predetermined voltage references, the analog voltage signal depending on the digital reference signal;
• a first resistor and a second resistor located outside the R-2R resistive ladder network and coupled in series between the positive and negative dc-power-supply terminals to receive the first and second predetermined voltage references;
• a third resistor located outside the R-2R resistive ladder network and coupled between the output terminal of the R-2R resistive ladder network and the second resistor located outside the R-2R resistive ladder network;
• and
• a conversion output terminal coupled to a junction between the second and third resistors located outside the R-2R resistive ladder network, the analog reference signal appearing at the conversion output terminal.