Dual threshold comparator circuit

For detecting transitions of an input signal between first and second states by comparison of the input signal to first and second adaptively derived threshold voltages, a circuit comprising:

• positive and negative peak detector circuits connected to the input signal source, said peak detector circuits providing output signals equal to the positive and negative peak voltages, respectively, of the input signal during two successive cycles, each of said peak detector circuits including a reset input;
• a slope detector circuit connected to the input signal source for providing an output voltage having a first value for positive slopes and a second value for negative slopes;
• an adaptive threshold-establishing circuit having a first input from said positive peak detector circuit, a second input from said negative peak detector circuit and a common output, said threshold-establishing circuit including a first impedance connecting said first input to said common output, a second impedance connecting said second input to said common output and means responsive to the value of the output from said slope detector circuit for changing the effective value of one of said impedances;
• comparator means connected to the input signal source and to the common output of said threshold-establishing circuit, said comparator means providing an output having a first state when the input signal is greater than the signal on the common output and a second state when the input signal is less than the signal on the common output;
• and
• means for applying the output of said comparator means to the reset inputs of said peak detector circuits to reset each peak detector whenever the comparator output changes to a state corresponding to the output of the peak detector to be reset.