Modulator circuits

Claim 1

A MODULATOR CIRCUIT COMPRISING FIRST, SECOND, THIRD AND FOURTH AMPLIFIERS, EACH HAVING FIRST AND SECOND INPUTS AND AN OUTPUT AN EACH BEING ADAPTED TO AMPLIFY NEGATIVELY SIGNALS APPLIED TO THE FIRST INPUT AND TO AMPLIFY POSITIVELY SIGNALS APPLIED TO THE SECOND INPUT, BIASING MEANS FOR EACH OF SAID AMPLIFIERS, A SOURCE OF MODULATING SIGNAL, A SOURCE OF CARRIER SIGNAL, MEANS TO APPLY SAID CARRIER SIGNAL TO THE FIRST INPUT OF THE FIRST AMPLIFIER AND TO THE SECOND INPUT OF THE SECOND AMPLIFIER, A SOURCE OF RECERENCE POTENTIAL, MEANS CONNECTING THE FIRST INPUT OF THE FOURTH AMPLIFIER AND THE SECOND INPUT OF THE THIRD AMPLIFIER TO SAID SOURCE OF REFERENCE POTENTIAL, MEANS TO APPLY THE MODULATING SIGNAL TO THE REMAINING INPUTS OF THE FIRST, SECOND, THIRD AND FOURTH AMPLIFIERS, MEANS FORMING A FIRST SIGNAL AS THE SUM OF THE OUTPUTS OF THE FIRST AND SECOND AMPLIFIERS, MEANS FORMING A SECOND SIGNAL AS THE SUM OF THE OUTPUTS OF THE THIRD AND FOURTH AMPLIFIERS, AND A DIFFERENCE AMPLIFIER FORMING AN OUTPUT SIGNAL AS THE DIFFERENCE BETWEEN SAID FIRST AND SECOND SIGNALS.