Signal holding circuit
First Claim
1. A signal holding circuit comprising:
- an audio signal input terminal;
an audio signal output terminal;
an emitter follower transistor for introducing an audio signal supplied to said input terminal to said output terminal;
a constant current source transistor connected to an emitter of said emitter follower transistor for defining an emitter current thereof;
a control signal input terminal for receiving a control signal;
control circuit means connected between said control signal input terminal and the base of said emitter follower transistor and said constant current source transistor, and operative to substantially cut off said emitter follower transistor and substantially cut off said constant current source transistor when a control signal is applied to said control signal input terminal; and
a hold capacitor connected in parallel with said constant current source transistor, said audio signal being supplied to said hold capacitor when said emitter follower transistor is conducting, said hold capacitor functioning to hold an output level at the emitter of said emitter follower transistor to a level at a moment immediately before the cut off of said emitter follower transistor in accordance with the supplied audio signal when said emitter follower transistor is cut off.
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Accused Products
Abstract
A signal holding circuit is disclosed in which a parallel circuit of a constant current source circuit comprising a transistor having a constant voltage supplied to a base thereof and a hold capacitor is connected to an emitter follower transistor, a first control transistor is connected between a base of the emitter follower transistor and ground, a second control transistor is connected between the base of the transistor of the constant current source circuit and ground, and a control pulse corresponding in time to a duration of the pulsive noise is applied to the bases of the first and second control transistors to render the first and second control transistors conductive only during the application of the control pulse so that a charging time constant of the hold capacitor during the conduction of the emitter follower transistor is reduced and a discharging time constant of the hold capacitor during the cutoff of the emitter follower capacitor is increased.
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Citations
16 Claims
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1. A signal holding circuit comprising:
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an audio signal input terminal; an audio signal output terminal; an emitter follower transistor for introducing an audio signal supplied to said input terminal to said output terminal; a constant current source transistor connected to an emitter of said emitter follower transistor for defining an emitter current thereof; a control signal input terminal for receiving a control signal; control circuit means connected between said control signal input terminal and the base of said emitter follower transistor and said constant current source transistor, and operative to substantially cut off said emitter follower transistor and substantially cut off said constant current source transistor when a control signal is applied to said control signal input terminal; and a hold capacitor connected in parallel with said constant current source transistor, said audio signal being supplied to said hold capacitor when said emitter follower transistor is conducting, said hold capacitor functioning to hold an output level at the emitter of said emitter follower transistor to a level at a moment immediately before the cut off of said emitter follower transistor in accordance with the supplied audio signal when said emitter follower transistor is cut off. - View Dependent Claims (2, 3)
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4. A signal holding circuit comprising:
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an audio signal input terminal; an audio signal output terminal; an emitter follower transistor for introducing an audio signal supplied to said input terminal to said output terminal; a constant current source transistor connected to an emitter of said emitter follower transistor for defining an emitter current thereof; a control pulse input terminal for receiving a control pulse when a pulsive noise is superimposed on said audio signal, said control pulse corresponding in time to said pulsive noise and having a pulse width equal to or wider than a pulse width of said pulsive noise; a first control transistor adapted to be forward biased into conduction by said control pulse supplied to said control pulse input terminal to ground a base of said emitter follower transistor to substantially cut off said emitter follower transistor, a second control transistor adapted to be forward biased into conduction by the control pulse supplied to said control pulse input terminal to ground a base of said constant current source transistor to substantially cut off said constant current source transistor; and a hold capacitor connected between the emitter of said emitter follower transistor and A.C.-wise ground, said audio signal being supplied to said hold capacitor when said emitter follower transistor is conductive, said hold capacitor functioning to hold an output level at the emitter of said emitter follower transistor to a level at a movement immediately before the cutoff of said emitter follower transistor in accordance with said audio signal supplied to said hold capacitor when said emitter follower transistor is cut off. - View Dependent Claims (5)
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6. A signal holding circuit comprising:
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an audio signal input terminal; an audio signal output terminal; an emitter follower transistor for introducing an audio signal supplied to said input terminal to said output terminal; a constant current source transistor connected to an emitter of said emitter follower transistor for defining an emitter current thereof; a control D.C. signal input terminal for receiving a control D.C. signal; a first control transistor adapted to be forward biased into conduction by the control D.C. signal supplied to said control D.C. signal input terminal to ground a base of said emitter follower transistor to substantially cut off said emitter follower transistor; a second control transistor adapted to be forward biased into conduction by the control D.C. signal supplied to said control D.C. signal input terminal to ground a base of said constant current source transistor to substantially cut off said constant current source transistor; and a hold capacitor connected between said emitter of said emitter follower transistor and A.C.-wise ground, said audio signal being supplied to said hold capacitor when said emitter follower transistor is conductive, said hold capacitor functioning to hold an output level at the emitter of said emitter follower transistor to a level at a moment immediately before the cut off of said emitter follower transistor in accordance with the audio signal supplied to said hold capacitor when said emitter follower transistor is cut off.
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7. A signal holdingcircuit comprising:
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a transistor of the type which includes a collecting electrode, an emitting electrode, and a control electrode and in which the conductivity between said collecting electrode and said emitting electrode is controlled by an input signal applied to said control electrode, and an output is produced from said emitting electrode; biasing means connected to said control electrode of said transistor to apply a bias potential to said transistor to keep said transistor normally conductive; a hold capacitor connected to said emitting electrode of said transistor; impedance circuit means connected to constitute a parallel discharge circuit to said hold capacitor and normally assuming a low impedance; and control circuit means responsive to the application of a control pulse which sustains for a predetermined period during which the input signal is to be blocked to change the bias potential applied to said transistor by said biasing means to a potential to substantially cut off said transistor and cause said impedance circuit means to assume a high impedance during the sustained period of said control pulse. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. A signal holding circuit comprising:
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a transistor of the type which includes a collecting electrode, an emitting electrode, and a control electrode and in which the conductivity between said collecting electrode and said emitting electrode is controlled by an input signal applied to said control electrode, and an output is produced from said emitting electrode; biasing means connected to the control electrode of said transistor to apply a bias potential to said transistor to keep said transistor normally conductive; a hold capacitor connected between said emitting electrode of said transistor and A.C.-wise ground; a constant current current source transistor connected to said emitting electrode of said transistor for defining an emitting electrode current thereof; control circuit means responsive to the application of a control signal which sustains for a predetermined period during which the input signal is to be blocked to change the bias potential of said transistor to a potential to substantially cut off said transistor and cause said constant current transistor to substantially cut off during the sustained period of said control signal. - View Dependent Claims (15)
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16. A signal holding circuit comprising:
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an emitter follower transistor of the type which includes a collector electrode, an emitter electrode, and a base electrode and in which the conductivity between said collector electrode and said emitter electrode is controlled by an input signal applied to said base electrode, and an output is produced from said emitter electrode; a constant current source transistor connected to an emitter electrode of said emitter follower transistor for defining an emitter current thereof; a control signal input terminal for receiving a control signal; a first control transistor adapted to be forward biased into conduction by the control signal supplied to said control signal input terminal to ground a base of said emitter follower transistor to substantially cut off said emitter follower transistor; second control transistor adapted to be forward biased into conduction by the control signal supplied to said control signal input terminal to ground a base electrode of said constant current source transistor to substantially cut off said constant current source transistor; and a hold capacitor connected between said emitter electrode of said emitter follower transistor and A.C.-wise ground, said input signal being supplied to said hold capacitor when said emitter follower transistor is conductive, said hold capacitor functioning to hold an output level at the emitter electrode of said emitter follower transistor to a level at a moment immediately before the cut off of said emitter follower transistor in accordance with the input signal supplied to said hold capacitor when said emitter follower transistor is cut off.
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Specification