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# Logarithmic Analog To Digital Converter

IP.com Disclosure Number: IPCOM000094726D
Original Publication Date: 1965-May-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 32K

IBM

## Related People

Sierra, HM: AUTHOR

## Abstract

In this accurate analog-to-digital converter, the various stages of the converter do not directly operate upon the input signal. Instead, the input signal is first amplified exponentially by amplifier 10. That is, the input signal S is converted into a signal having magnitude 2's'. The converter has three stages which respectively generate a three-digit binary number. This has digits D1, D2 and D3 which represent the magnitude of the input signal S.

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Logarithmic Analog To Digital Converter

In this accurate analog-to-digital converter, the various stages of the converter do not directly operate upon the input signal. Instead, the input signal is first amplified exponentially by amplifier 10. That is, the input signal S is converted into a signal having magnitude 2's'. The converter has three stages which respectively generate a three-digit binary number. This has digits D1, D2 and D3 which represent the magnitude of the input signal S.

Each stage includes potentiometer 13, comparator 14 and logical circuit 15. Potentiometer 13 in each stage divides the voltage from a previous stage in a logarithmic fashion. Each comparator 14 compares the output of the associated potentiometer tapoff to a signal of one volt. The comparator generates an output if the comparison indicates that the output of the potentiometer is greater than one volt. Each logical circuit 15 has three inputs a, b and c and an output d. The logical circuitry performs the following operations. In input c is activated, output d is set equal to input b. If input c is not activated, output d is set equal to input a.

Each stage in the converter is identical with the exception that the tapoff point of the associated potentiometer differs. in each stage. In the three stages shown, the tapoff points generate voltages that are .250, .500 and .707 of the input. If additional stages are added, the tapoff points generate voltages that are
.841 and .917, etc.,...