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Amplifier Gain Selection With Noise Tolerance

IP.com Disclosure Number: IPCOM000093483D
Original Publication Date: 1967-Oct-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

McKeon, A: AUTHOR

Abstract

In analog-to-digital converters having a variable gain input signal amplification apparatus, the ADC can be overloaded as a result of inserting improper, i.e., too high, gain into circuit with the input signal. Improper gain selection can be caused by noise associated with the input analog signal.

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Amplifier Gain Selection With Noise Tolerance

In analog-to-digital converters having a variable gain input signal amplification apparatus, the ADC can be overloaded as a result of inserting improper, i.e., too high, gain into circuit with the input signal. Improper gain selection can be caused by noise associated with the input analog signal.

ADC 10 converts analog signals from input signal generator 12 into digital numbers. The input signals must be built up to an optimum proportion of the full- scale input for ADC 10. This is accomplished with variable gain amplification apparatus 14 comprising amplifier 16, associated feedback resistors 18, 20, and 22, and switches 24, 26, and 28. A first conversion cycle is implemented with amplifier 16 set to a gain of unity by closing switch 24. Decoder 32 senses the higher order digits generated by ADC 10 so as to select the proper gain for amplifier 16. This selection is implemented by closing switches 24, 26, and 28 as necessary by signals on line 30.

If amplifier 16 normally has two gain ranges, selected by switches 24 and 28, the adverse effect of noise in the input signal can be compensated for by providing an additional gain range embodied in resistor 20 and selected by switch 26. For example, if switches 24 and 28 select gains of unity and two respectively, a range of unity plus some factor is provided. That factor is numerically equal to the maximum amount of noise to be expected in the input signal. If the noise i...