Sensitive threshold signal detector circuit

Claim 2

A signal threshold detector comprising in combination an input terminal and an output terminal, an input stage comprising a first transistor having an emitter, a collector and a base electrode, a capacitor connecting said input terminal to the base of said first transistor, a resistor coupling the base of said first transistor to a source of supply potential, a flip-flop circuit comprising second and third transistors each having an emitter, a collector and a base electrode, the base of said second transistor being connected to the collector of said third transistor and the base of said third transistor being connected to the collector of said second transistor, a pair of resistors coupling respectively the collectors of said second and third transistors to said source of supply potential, the collector of said first transistor being connected to the emitter of said second transistor, the emitters of said first and third transistors being connecTed to ground potential, reset means comprising a reset terminal and a pair of current paths, each path including in series a resistor and a diode, said current paths connecting the respective bases of said first and second transistors in common to said reset terminal, an output stage comprising a fourth transistor having an emitter, a collector and a base electrode, a resistor coupling the base of said fourth transistor to the collector of said third transistor, a resistor coupling the collector of said fourth transistor to said source of supply potential, the emitter of said fourth transistor being connected to ground potential, said output terminal of said threshold detector appearing at the collector of said fourth transistor.

Claim 3

A signal threshold detector comprising in combination an input terminal and an output terminal, an input current amplifying stage and a latch circuit capable of assuming either of two stable conditions, means coupling said input stage to said latch circuit, a capacitor coupling said input terminal to said input stage, said input stage being normally in a conducting state and said latch circuit being in a first of said stable conditions, the degree of conduction of said input stage being a function of the instantaneous amplitude of an input electrical signal and the electrical charge on said capacitor, said input stage being driven to a nonconducting state by an input signal of predetermined amplitude and polarity, said latch circuit being switched to the second of said stable conditions in response to the cessation of conduction in said input stage, the change in signal level occurring on said detector output terminal in response to the switching of said latch circuit from said first to said second stable condition being indicative of the attainment of a threshold level by said input signal, said latch circuit second stable condition and the corresponding signal level on said detector output terminal being unaffected by the subsequent conduction of said input stage, reset control means coupled in common to both said input stage and to said latch circuit, said reset control means being adapted to be energized during said subsequent conduction of said input stage for switching said latch circuit from said second to said first stable condition, the signal on said detector output terminal returning to its initial level in response to the last-mentioned switching of said latch circuit.

Claim 4

A signal threshold detector comprising in combination an input terminal and an output terminal, an input current amplifying stage and a latch circuit capable of assuming either of two stable conditions, means coupling said input stage to said latch circuit, a capacitor coupling said input terminal to said input stage, said input stage being normally in a conducting state and said latch circuit being in a first of said stable conditions, the degree of conduction of said input stage being a function of the instantaneous amplitude of an input electrical signal and the electrical charge on said capacitor, said input stage being driven to a nonconducting state by an input signal of predetermined amplitude and polarity, said latch circuit being switched to the second of said stable conditions in response to the cessation of conduction in said input stage, the change in signal level occurring on said detector output terminal in response to the switching of said latch circuit from said first to said second stable condition being indicative of the attainment of a threshold level by said input signal, said latch circuit second stable condition and the corresponding signal level on said detector output terminal being unaffected by the subsequent conduction of said input stage, reset control means coupled in common to both said input stage and to said latch circuit, said reset control means being adapted to be energized during said subsequent conduction of said input stage for switching said latch circuit from said second to said first stable condition, the signal on said detector output terminal returning to its initial level in response to the last-mentioned switching of said latch circuit.

Claim 5

A signal threshold detector as defined in claim 2 further characterized in that said input current amplifying stage has an input, an output and a control electrode, said capacitor being connected between said detector input terminal and the control electrode of said input amplifying stage, impedance means for coupling said input stage control electrode to a source of supply potential, said latch circuit comprising first and second current amplifying devices, each of said latch circuit devices having an input, an output and a control electrode, said latch circuit devices being connected in a cross-coupled flip-flop configuration wherein the control electrode of said first device is coupled to the output electrode of said second device and the control electrode of said second device is coupled to the output electrode of said first device, impedance means coupling respectively the output electrodes of said latch circuit devices to said source of supply potential, the output electrode of said input stage being connected to the input electrode of said first latch circuit device, the respective input electrodes of said input stage and said second latch circuit device being connected to a source of reference potential, said reset control means comprising a reset terminal and a pair of current paths, each path including in series impedance means and a diode, said circuit paths connecting the respective control electrodes of said input stage and said first latch circuit device in common to said reset terminal.

Claim 6

A signal threshold detector as defined in claim 3 further including an output buffer stage, said output buffer stage comprising a current amplifying device having an input, an output and a control electrode, impedance means coupling the control electrode of said output buffer stage device to the output electrode of said second latch circuit device, impedance means coupling the output electrode of said output buffer stage device to said source of supply potential, said input electrode of said output buffer stage device being connected to said source of reference potential, said output terminal of said threshold detector corresponding electrically to the output electrode of said output buffer stage device.

Claim 7

A signal threshold detector as defined in claim 4 wherein said current amplifying stages and devices are transistors of NPN conductivity type, and said input, output and control electrodes are respectively emitter, collector and base electrodes.