A test circuit for measuring MOSFET threshold voltage mismatch

A new test circuit is proposed for evaluating MOSFET threshold voltage mismatch. This test circuit consists of many parallel-connected unit cells, in which two MOSFETs are serially-connected each other and the node between them is connected to common wiring through a switch. The threshold voltage mismatch for the two MOSFETs is derived from the DC currents flowing through this test circuit when the switch being ON and OFF. It is shown that the quantity corresponding to the standard deviation of the threshold voltage is derived from the peak value of the ON/OFF current ratio. Experimental test chips, which include the test circuits having different design channel width, design channel length, MOSFET number and channel conductivity, are developed. The reasonable results are obtained from them.