Transistorized Multiplier and Divider and Its Applications

The inverse pair of logarithmic and exponential functions obtained from current voltage characteristics of junction transistors have been combined here to devise a direct method of analog multiplication and division which has an inherent tendency of self-compensation for the effects of temperature variation and also of mutual cancellation of nonlinear distortion arising in the individual stages. Experimental curves for both the operations show an accuracy of 2 per cent over a range of one and one-half decades in multiplication and about two decades in division. It has further been shown how this system may be used with comparative advantages to realize ac power and root law amplifiers, volume compressors and volume expandors of compandor systems, linear amplitude modulators and amplitude stabilizers. The experimental observations of ac nonlinear amplifiers designed to follow square and square root law response functions show that the respective characteristics hold good within an accuracy of 2 per cent over a range of 50 db. The use of these inverse relationships as a conventional 2 to 1 compressor followed by an expandor yields over-all compandor characteristics having a linearity over a range of 55 db with a maximum deviation of about 0.6 db from a straight line appearing only at the extreme end of the dynamic range. The analog multiplication has further been used to produce a linear amplitude modulation of about 95 per cent.