Video signalling processing apparatus

Claim 2

A peak detecting circuit including in combination: a differential amplifier means including a first transistor, a second transistor, and constant current means connected to the emitters of the first and second transistors and operable to maintain constant the total current flowing through the first and second transistors independent of signals applied at their bases; said differential amplifier means being operable to cause the voltage at the collector of the second transistor to increase with increasing current flow through the first transistor; transistor circuit means including a third transistor having its emitter connected to the base of the first transistor, and a fourth transistor having its emitter connected to the base of the second transistor; said transistor circuit means being operable to cause increased current flow through the first transistor when the voltage at the base of the third transistor is greater than the voltage at the base of the fourth transistor and being operable to cause increased current flow through the second transistor when the voltage at the base of the fourth transistor is greater than the voltage at the base of the third transistor; emitterfollower means including a first emitter-follower transistor having its base connected to the collector of the second transistor, and a second emitter-follower transistor having its base connected to the emitter of the first emitter-follower transistor and its emitter connected through a feedback resistance to the base of the fourth transistor; and a capacitance having one terminal connected to a source of reference potential and the other terminal connected to the emitter of the second emitter-follower transistor; said emitter-follower means being operable to cause current flow therethrough into the capacitance when the voltage at the collector of the second transistor increases.

Claim 3

A comparator circuit including in combination: a differential amplifier means including a first amplifier transistor of one conductivity type, and a second amplifier transistor of the one conductivity type; constant current means including a first current control transistor of the opposite conductivity type having its collector connected through an impedance to a first source of reference potential and its emitter connected to a second source of reference potential, a second current control transistor of the one conductivity type having its emitter connected to the collector of the first current control transistor and its collector connected to the base of the first current control transistor, current multiplying means including a third current control transistor of the opposite conductivity type having its base connected to the base of the second current control transistor, its emitter connected to the second source of reference potential, and its collector connected to the bases of the first and second amplifier transistors, whereby the voltage drop across the base-emitter junctions of the third and second current control transistors clamps the voltage at the collector of the first current control transistor thereby fixing the current flow in the collector of the first current control transistor and consequently the base current of the second current control transistor, which current flowing into the current multiplying means controls current flow in the collector circuit of the third current control transistor; output means connected to the collectors of the first and second amplifier transistors including an output transistor of the opposite conductivity type having its base connected to the collector of the first amplifier transistor, its emitter connected to the second source of reference potential, and its collector connected to an output connection, and current source means connected to the collectors of the first and second amplifier transistors, the base of the output transistor, and the second source of reference potential, said current source means being operable to bias the output transistor to conduction when current flow through the first amplifier transistor is greater than current flow through the second amplifier transistor; said differential amplifier means also including a first input means connected to the emitter of the first amplifier transistor and having a first input connection, and a second input means connected to the emitter of the second amplifier transistor and having a second input connection, said first and second input means being operable to cause greater current flow through the first amplifier transistor than through the second amplifier transistor when the voltage at the first input connection is greater than the voltage at the second input connection.

Claim 4

A comparator circuit including in combination: a differential amplifier means including a first amplifier transistor of one conductivity type, and a second amplifier transistor of the one conductivity type; constant current means including a first current control transistor of the opposite conductivity type having its collector connected through an impedance to a first source of reference potential and its emitter connected to a second source of reference potential, a second current control transistor of the one conductivity type having its emitter connected to the collector of the first current control transistor and its collector connected to the base of the first current control transistor, current multiplying means including a third current control transistor of the opposite conductivity type having its base connected to the base of the second current control transistor, its emitter connected to the second source of reference potential, and its collector connected to the bases of the first and second amplifier transistors, whereby the voltage drop across the base-emitter junctions of the third and second current control transistors clamps the voltage at the collector of the first current control transistor thereby fixing the current flow in the collector of the first current control transistor and consequently the base current of the second current control transistor, which current flowing into the current multiplying means controls current flow in the collector circuit of the third current control transistor; output means connected to the collectors of the first and second amplifier transistors including an output transistor of the opposite conductivity type having its base connected to the collector of the first amplifier transistor, its emitter connected to the second source of reference potential, and its collector connected to an output connection, and current source means connected to the collectors of the first and second amplifier transistors, the base of the output transistor, and the second source of reference potential, said current source means being operable to bias the output transistor to conduction when current flow through the first amplifier transistor is greater than current flow through the second amplifier transistor; said differential amplifier means also including a first input means connected to the emitter of the first amplifier transistor and having a first input connection, and a second input means connected to the emitter of the second amplifier transistor and having a second input connection, said first and second input means being operable to cause greater current flow through the first amplifier transistor than through the second amplifier transistor when the voltage at the first input connection is greater than the voltage at the second input connection.

Claim 5

A comparator circuit in accordance with claim 2 wherein: said first input means includes a first input transistor of the opposite conductivity type having its base connected to the first input connection, its emItter connected to the emitter of the first amplifier transistor, and its collector connected to a third source of reference potential; said second input means includes a second input transistor of the opposite conductivity type having its base connected to the second input connection, its emitter connected to the emitter of the second amplifier transistor, and its collector connected to the third source of reference potential; and said current source means includes a current source transistor of the opposite conductivity type having its collector connected to the collector of the first amplifier transistor and to the base of the output transistor, its base connected to the collector of the second amplifier transistor, and its emitter connected to the second source of reference potential, and a diode connected between the collector of the second amplifier transistor and the second source of reference potential so as to be forward biased when current flows in the collector circuit of the second amplifier transistor, said diode having substantially the same forward voltage drop characteristics as the base-emitter junction of said current source transistor.