Heisenberg constraints on mesoscopic and molecular amplifiers
  Heisenberg uncertainty relations for current components impose constraints on the performance of linear amplifiers. Here we derive such constraints for amplifiers in which the input signal modulates a bias current in order to produce an amplified output. These amplifiers include transistors, macroscopic, mesoscopic, or molecular, operated as linear amplifiers. 
U. Gavish, B. Yurke and Y. Imry