Magneto-resistance type contactless rotational angle detecting apparatus

An apparatus for detecting a rotational angle of a rotatable body comprising:

• an electric power source;
• a magnet for producing a fixed magnetic field and a supporting member fixedly supporting said magnet;
• a bridge circuit placed in said fixed magnetic field and having a first arm, a second arm having one end connected in series with said first arm, a third arm and a fourth arm having one end connected in series with said third arm, a junction point between said first arm and said third arm and a junction point between said second arm and said fourth arm being connected across said electric power source, each of said arms including a magneto-resistance element which varies the electric resistance in accordance with the direction of said magnetic field, and said first and fourth arms further including respective resistors having electric resistances which keep one voltage signal developed across said fourth arm larger than the other voltage signal developed across said second arm;
• a voltage-current converter connected to said bridge circuit for producing an electric current proportional to the difference between said one and the other voltage signals;
• a current-voltage converter connected to said voltage-current converter for producing an output voltage signal proportional to said electric current;
• and
• means for rotating said bridge circuit in synchronized relation with said rotatable body.