Impedance measuring semiconductor circuit and blood-sugar level meter

An impedance measuring semiconductor circuit comprising:

• a first test strip including a first one-side terminal and a first different-side terminal, the first test strips including a first specimen;
• a second test strip including a second one-side terminal and a second different-side terminal, the second test strips including a second specimen;
• an operational amplifier;
• a resistance coupled between a negative input terminal of the operational amplifier and an output terminal of the operational amplifier;
• a first D/A converter coupled to a positive input terminal of the operational amplifier;
• a first switch placed between the first one-side terminal of the first test strip and the negative input terminal of the operational amplifier;
• a second switch placed between the second one-side terminal of the second test strip and the negative input terminal of the operational amplifier;
• an A/D converter that is coupled with the output terminal of the operational amplifier, the first one-side terminal of the first test strip, and the second one-side terminal of the second test strip, and that measures an output voltage from the operational amplifier, a first one-side terminal voltage as a terminal voltage of the first one-side terminal, and a second one-side terminal voltage as a terminal voltage of the second one-side terminal;
• and
• a buffer amplifier that includes an output terminal and a negative input terminal coupled to each other;
• a second D/A converter coupled to a positive input terminal of the buffer amplifier;
• and
• a controller that 1) sets i) the first terminal-to-terminal voltage between the first one-side terminal and the first different-side terminal and ii) the second terminal-to-terminal voltage between the second one-side terminal and the second different-side terminal to a target value to measure a first substance in the first specimen and the second specimen, 2) varies the target value in a stepwise manner to measure a second substance in the first specimen and the second specimen, and 3) controls at least one of an output voltage from the first D/A converter and an output voltage from the second D/A converter based on the first terminal-to-terminal voltage or the second terminal-to-terminal voltage,
• wherein the first terminal-to-terminal voltage and the second terminal-to-terminal voltage are calculated using the first one-side terminal voltage and the second one-side terminal voltage measured by the A/D converter, respectively,
• wherein the output voltage from the operational amplifier is used to measure first impedance of the first specimen and second impedance of the second specimen.