US Patent 7446554 Direct current measuring apparatus and limiting circuit

A direct current measuring apparatus includes a voltage generating part generating a voltage to be applied to a load being a measuring object; a current limiting part limiting a current flowing in the load to a set value; and an output terminal connected to the load. The current limiting part includes a D/A converter, a positive side limiting circuit, a D/A converter and a negative side limiting circuit. The positive side limiting circuit includes a negative feedback loop. The negative feedback loop includes a capacitor and a buffer circuit besides the feedback resistance. An output of the positive side limiting circuit positive side limiting circuit is connected to a non-inverting input terminal of the main amplifier through a diode.