Differential amplifiers with enhanced linearity and temperature compensation

This paper implements a “multi-tanh principle” to linearize the bipolar differential amplifiers by offsetting the transfer function of the differential pairs and connection them in parallel. The principle is analyzed in detail and the optimum 3.75 and 2.9 offset ratio is found for a double and a 4-cell linearized differential amplifier. The resulted 4-cell linearized amplifier achieves an extremely linear ±20mV dynamic range within less than 0.1 dB ripple. The structure is shouldable for further expansion for wider linear operation. Temperature dependence is discussed and compensation from 250K-400K is realized by implementing the transistor size ratio, the Widlar current source and MOS voltage shift cell. Such differential amplifier with high linearity and insensitivity to stress will be suitable for high frequency situation or accurate gain control in varies of industrial applications.