Design of a NP ν N Si microwave transistors with wide output spaces

Si NPvN microwave transistors have been designed and fabricated with the objective of maximizing power gain by widening the collector depletion region (output space) far beyond that which gives maximum fT. For maximum power gain the output space delay angle should be roughly 1/8 of an rf cycle and consequently the optimum output spacing depends on the operating frequency. Increasing the output space leads to increased power gain at the expense of lower fT and higher output impedance.