A sinh resistor and its application to tanh linearization

We present a novel and simple subthreshold tunable resistor (sinhR) which exhibits a sinh I-V characteristic. This compact 8-transistor circuit generates an output current that is proportional to the sinh of its input differential voltage and has an offset-free characteristic, i.e., zero current at zero differential voltage, like a real resistor. In a 1.5-μm CMOS chip implementation, we achieved a common-mode rejection ratio (CMRR) of 46 dB. As an example application, we use the expansive properties of our sinhR to linearize the compressive properties of a tanh differential pair by degeneration and cancel all nonlinearities up to fifth order. We demonstrate good agreement between theory and experimental results.