A unidirectional amplifier with Esaki diodes

Two Esaki diodes can furnish unidirectional amplification when used in conjunction with a Hall-effect isolator. The input and output impedances of this amplifier are greater than the absolute value of the negative resistance of the diodes by a factor which is proportional to the voltage gain. The voltage gain-bandwidth product of such an amplifier is , where gTis determined by the isolator and RC is the usual RC time constant of the Esaki diodes. Typically, gTis between 0.1 and 1. If one of the diodes is removed, the remaining network still amplifies unilaterally, but the impedance at the diode-less end drops to that of the isolator alone. In addition, a Hall-effect gyrator or circulator can be made essentially lossless by the addition of Esaki diodes.