Choice between FETs or Bipolar Transistors and Optimization of Their Working Points in Low Noise Preamplifiers for Fast Pulse Processing. Theory and Experimental Results

Theoretical and experimental investigation has been carried out to determine the best working conditions of single or parallel combinations of field-effect or bipolar transistors in low noise preamplifiers for processing times in the 10 ns range. The effects of diffusion capacitance and base spreading resistance in bipolar transistors have been put into evidence and a way of reducing the noise due to the latter is suggested and experimentally demonstrated.