circuits comprising : digital - to - amplitude converter , comprising : binary weighted switching transistors , each having gate coupled to amplitude control bit acb , and wherein the drain of each of the bwsts are connected together and wherein the source of each of the bwsts are connected together ; transistor m 1 having gate coupled to input signal and first bias voltage bv 1 and source coupled to the drains of the bwsts ; transistor m 2 having gate coupled to bv 2 and source coupled to the drain of m 1 ; transistor m 3 having gate coupled to bv 3 and source coupled to the drain of m 2 ; transistor having gate coupled to bv 4 , source coupled to the drain of m 3 ; and inverter having input coupled to another acb and having output coupled to the output of the dac and the drain of m 4 .