CLAMP CIRCUIT
First Claim
1. A clamp circuit which is incorporated in an IC and clamps an input voltage inputted into an input terminal of said IC, comprising:
- an input voltage detecting circuit for outputting a detected voltage, wherein a first resistance circuit and a first transistor in a form of a source follower or emitter follower are connected in series between a first and second supply line and said input voltage is inputted into a control terminal of said first transistor and said detected voltage is outputted from said first resistor circuit;
a reference voltage generating circuit for outputting a reference voltage, wherein a second resistance circuit and a second transistor in a form of a source follower or emitter follower are connected in series between said first and second supply line and a voltage of said second supply line is inputted into a control terminal of said second transistor and said reference voltage is outputted from said second resistor circuit;
a comparator for outputting an instruction signal instructing to clamp said input signal, when said detected voltage goes across said reference voltage on the basis of comparison of said detected voltage with said reference voltage; and
a switching circuit connected between said signal input terminal and said first or second supply line, said switching circuit being switched on, under such a condition that said instruction signal is outputted from said comparator.
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Accused Products
Abstract
The clamp circuit clamps an input voltage at prescribed higher and lower clamp voltages which are stabilized under a temperature fluctuation. Transistors Q12 and Q14 are switched on in their linear region. In a lower voltage clamp circuit 18, an Vin detecting circuit 20 outputs Va1 by level-shifting Vin by Q13 and voltage-divides by series resistance circuit 23 the level-shifted Vin, while a reference voltage generating circuit 21 outputs Vr1 by level-shifting 0 V by Q15 and voltage-divides by series resistance circuit 25 the level-shifted voltage. Q11 is switched on, when a comparator 22 determines that Va1 descends and goes across Vr1. Here, Q12 is of the same characteristics as Q14, while Q13 is of the same characteristics as Q15. Further, the resistance of the circuits 23 is the same as that of the circuit 25. The higher voltage clamp circuit 19 is similar to the circuit 18.
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Citations
6 Claims
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1. A clamp circuit which is incorporated in an IC and clamps an input voltage inputted into an input terminal of said IC, comprising:
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an input voltage detecting circuit for outputting a detected voltage, wherein a first resistance circuit and a first transistor in a form of a source follower or emitter follower are connected in series between a first and second supply line and said input voltage is inputted into a control terminal of said first transistor and said detected voltage is outputted from said first resistor circuit;
a reference voltage generating circuit for outputting a reference voltage, wherein a second resistance circuit and a second transistor in a form of a source follower or emitter follower are connected in series between said first and second supply line and a voltage of said second supply line is inputted into a control terminal of said second transistor and said reference voltage is outputted from said second resistor circuit;
a comparator for outputting an instruction signal instructing to clamp said input signal, when said detected voltage goes across said reference voltage on the basis of comparison of said detected voltage with said reference voltage; and
a switching circuit connected between said signal input terminal and said first or second supply line, said switching circuit being switched on, under such a condition that said instruction signal is outputted from said comparator. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification