Differential amplifier circuit and electric charge control apparatus using differential amplifier circuit

An electric charge control apparatus, comprising:

• an electric charge current detection circuit configured to detect an electric charge current supplied to a secondary battery through an electric charge current detection use resistance by converting a both end voltage of the electric charge current detection use resistance into a voltage with reference to a ground using a subtraction circuit having a differential amplifier circuit;
• wherein said secondary battery is electrically charged by controlling the electric charge current based on an output signal outputted from the electric charge current detection circuit, and
• wherein said differential amplifier circuit including:
• a first input transistor including a control electrode serving as a non-inversion input terminal;
• a second input transistor including a control electrode serving as an inversion input terminal, said second input transistor constituting a difference pair with the first input transistor;
• a bias current generation circuit section configured to generate a bias current flowing to the first and second input transistors;
• and
• an offset adjustment circuit section configured to adjust an input offset voltage appearing at said input terminals, said offset adjustment circuit section having an adjustment resistance formed from a first variable resistance inserted into a first current route connecting to the first input transistor, and a second variable resistance inserted into a second current route connecting to the second input transistor;
• wherein said bias current generation circuit section changes the bias current in accordance with a change in a value of the adjustment resistance and said bias current generation circuit section comprises:
• a bias current generation use resistance configured to change a value of its own resistance in proportion to a change in a value of the adjustment resistance;
• a current control circuit configured to control a current flowing to the bias current generation use resistance so that a voltage drop in the bias current generation use resistance becomes a prescribed amount;
• and
• a proportional current generation circuit configured to generate a current as a bias current in proportion to the current flowing from the current control circuit to the bias current generation use resistance.

A differential amplifier circuit, comprising:

• an offset adjustment circuit configured to adjust an input offset voltage across a difference pair formed by a non-inversion input transistor and an inversion input transistor by adjusting an adjustment resistance between the transistors;
• and
• a bias current generation circuit configured to generate a bias current that changes in accordance with a change in a value of the adjustment resistance flowing to the non-inversion and inversion input transistors, said bias current generation circuit comprising:
• a bias current generation use resistance configured to change a value of its own resistance in proportion to a change in a value of the adjustment resistance;
• a current control circuit configured to control a current flowing to the bias current generation use resistance so that a voltage drop in the bias current generation use resistance becomes a prescribed amount;
• and
• a proportional current generation circuit configured to generate a current as a bias current in proportion to the current flowing from the current control circuit to the bias current generation use resistance.