Patent ID: 7429856

Claim:
Voltage source measurement unit (VSMU) circuitry configured to measure current across a device under test (DUT 202 ), the DUT having a first terminal (high terminal 104 ) and a second terminal (low terminal 108 ), the VSMU circuitry comprising: a precision resistor Rm 114 ; and a first operational amplifier (OpA 2 106 ) configured with an output ( 107 ) to drive the high terminal 104 of the DUT 102 ; wherein the VSMU circuitry is configurable to cause current to be sunk from the low terminal 108 of the DUT 102 to a common sink via the precision resistor (Rm 114 ); the VSMU circuitry further comprising: a second operational amplifier (OpA 3 126 ) having a non-inverting input ( 124 ) configured to be connected to the low terminal ( 108 ) of the DUT ( 102 ), having an inverting input ( 130 ) configured to be connected to an output ( 128 ) of the second operational amplifier (OpA 3 126 ) and to a non-inverting input ( 132 ) of the first operational amplifier (OpA 2 106 ); and a differential amplifier (DiffA 1 136 ) having a non-inverting input ( 134 ) connected to the output 128 of the second operational amplifier (OpA 3 126 ), an inverting input ( 138 ) connected to receive a precision set voltage (Vin), and an output coupled to an inverting input ( 131 ) of the first operational amplifier (OpA 2 106 ).