Signal comparator

Claim 1

A SIGNAL COMPARATOR COMPRISING: (A) A SOURCE OF TIME VARYING SIGNALS IN WHICH THE MEANS VALUE OF THE INPUT SIGNAL OVER AN INTERVAL GREATER THAN THE FREQUENCY OF SAID INPUT SIGNAL HAS A VALUE WHICH IS SUBSTANTIALLY VARIABLE WITH TIME; (B) A FORWARD TRANSMISSION PATH HAVING: (1) AN INPUT TERMINAL CONNECTED TO SAID SIGNAL SOURCE, (2) AN OUTPUT TERMINAL, (3) COMPARISON MEANS CONNECTED BETWEEN SAID TERMINALS FOR COMPARING A PREDETERMINED CHARACTERISTIC OF THE INPUT SIGNALS WITH A SIMILAR CHARACTERISTIC OF A PRESELECTED WORKING POINT FOR SAID COMPARISON MEANS, (A) SAID COMPARISON MEANS PRODUCING COMPARISON OUTPUT SIGNALS HAVING A FIRST VALUE WHEN THE WORKING POINT CHARACTERISTIC IS SMALLER THAN THE INPUT CHARACTERISTIC AND A SECOND VALUE WHEN SAID WORKING CHARACTERISTIC IS LARGER THAN SAID INPUT CHARACTERISTIC, (4) AND COMBINING MEANS CONNECTED BTWEEN SAID INPUT TERMINAL AND SAID COMPARISON MEANS; (C) FEEDBACK MEANS CONNECTED TO FEED A PORTION OF THE SIGNALS IN SAID FORWARD PATH BACK TO SAID COMBINING MEANS, SAID COMBINING MEANS COMBINING THE FEEDBACK SIGNALS WITH THE INPUT SIGNALS TO REDUCE THE DRIFT COMPONENT IN SAID INPUT SIGNALS, SAID FEEDBACK MEANS INCLUDING: (1) DETECTION MEANS FOR DETECTING THE DRIFT AND THE DIRECTION OF DRIFT OF THE WORKING POINT AND FOR GENERATING DETECTION OUTPUT SIGNALS IN RESPONSE TO THE THUS DETECTED DRIFT, SAID DETECTION MEANS INCLUDING: AN EXTRACTION CIRCUIT, MEANS FOR CONNECTING THE INPUT SIGNAL SOURCE TO SAID EXTRACTING CIRCUIT ALONG WITH THE PORTION OF THE COMPARISON OUTPUT SIGNALS BEING FED BACK, SAID EXTRACTING CIRCUIT PRODUCING A POSITIVE VALUE OUTPUT WHEN THE FIRST COMPARISON OUTPUT SIGNAL IS FED BACK THERETO AND PRODUCING A NEGATIVE VALUE OUTPUT WHEN THE SECOND COMPARISON OUTPUT IS FED BACK THERETO, A SUMMING CIRCUIT FOR SUMMING SAID POSITIVE AND NEGATIVE OUTPUT VALUES OF THE EXTRACTING CIRCUIT AND A LOW PASS FILTER FOR PRODUCING THE DETECTION OUTPUT SIGNALS IN RESPONSE TO THE SUM OF SAID OUTPUTS, SAID LAST MENTIONED CONNECTING MEANS COMPRISING A SWITCH CONTROLLING DEVICE RESPONSIVE TO THE OUTPUT OF SAID COMPARISON MEANS; AND A PAIR OF SWITCHES CONTROLLED BY SAID DEVICE FOR THE COMPLEMENTARY MAKING AND BREAKING DEPENDENT UPON THE SAID COMPARISON SIGNAL, (2) AMPLIFICATION MEANS FOR AMPLIFYING THE DETECTION OUTPUT SIGNALS WHEREBY THE DRIFT OF THE WORKING POINT OF SAID COMPARISON MEANS IS MINIMIZED.