Current-measuring operational amplifier circuits

An electrical circuit coupleable to a load impedance and adapted to measure current comprising:

• an operational amplifier with an output port and at least two input ports including a noninverting input port and an inverting input port;
• means for coupling an input signal to said noninverting input port;
• a current-measuring impedance coupled between said output port and said load impedance;
• and
• feedback circuit means coupled from a circuit node between said current-measuring impedance and said load impedance to said inverting input port, said feedback circuit means further including a first voltage divider network and additionally including a second voltage divider network coupling said input signal to said noninverting input port,
• whereby a voltage generated across said current-measuring impedance is proportional to said current through said current-measuring impedance.

An electrical circuit coupleable to a load impedance and adapted to measure current comprising:

• an operational amplifier having an output port and at least two input ports including a noninverting input port and an inverting input port;
• means for coupling an input signal to said noninverting input port;
• a current measuring impedance coupled between said output port and a diode, said diode being coupled between said current measuring impedance and said load impedance;
• and
• feedback circuit means coupled from a circuit node between said diode and said load impedance to said inverting input port,
• whereby a voltage generated across said current-measuring impedance is proportional to said current through said current-measuring impedance.

An electrical circuit coupleable to a load impedance and adapted to measure current comprising:

• an operational amplifier having an output port and at least two input ports including a noninverting input port and an inverting input port;
• integrator circuit means coupleable between an input signal and said noninverting input port of said operational amplifier;
• a current-measuring impedance coupled between said output port and said load impedance;
• and
• a feedback circuit including a direct connection coupled from a circuit node between said current-measuring impedance and said load impedance to said inverting input port of said operational amplifier,
• whereby a voltage generated across said current-measuring impedance is proportional to said current through said current-measuring impedance.

An electrical bridge measuring circuit, comprising:

• a first and a second leg of a bridge circuit commonly coupled to a first circuit node;
• a third and fourth leg of the bridge circuit commonly coupled to a second circuit node;
• said first and third leg commonly coupled to a third circuit node and said second and fourth leg commonly coupled to a fourth circuit node;
• a voltage source coupled across said first and second circuit nodes;
• wherein said third and fourth legs of the bridge circuit respectively comprise impedance means;
• and
• wherein said first and second legs of the bridge circuit comprise respective amplifier circuits, each including an amplifier having an output port and at least two input ports, and wherein one input port of said two input ports of both said amplifiers are commonly connected to said first circuit node, impedance means coupled from said output port to said third and fourth circuit nodes, respectively, and respective feedback circuit means coupled from said third and fourth circuit node to the other input port of said two input ports of said amplifiers;
• and
• means coupled between the respective output ports of said amplifiers for detecting a voltage difference therebetween.