US 2002/0153927 A1Published application

Signal hold circuit

AssigneeTexas Instruments Incorporated

InventorYouhei Maruyama

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Abstract

A peak hold circuit that can operate to follow changes in peak value even if the changes are abrupt. The peak hold circuit (1) of the present invention has current control circuit (31), auxiliary switch element (25), and auxiliary constant current circuit (26). Current control circuit (31) counts the number of reference clock pulses RCK after output signal Vout becomes higher than analog voltage DI. When the number of clock pulses counted reaches a prescribed number or larger, auxiliary switch element (25) is turned on to operate auxiliary constant current circuit (26) to increase the amount of drop of output signal Vout per unit time. Consequently, even if output signal Vout becomes higher than the peak value of analog voltage DI, it is possible, by increasing the amount of drop of output signal Vout to make output signal Vout lower than analog voltage DI in a shorter amount of time than in the case in the conventional technology. In this way, output signal Vout can be changed to follow the peak value of analog voltage DI. The circuit can be modified to follow a bottom signal.

Claims5

Dependent claims

A signal hold circuit having the following:

a comparison circuit that compares an input signal with an output signal and outputs a comparison signal,
a capacitor used for generating the aforementioned output signal,
a first constant current circuit used for supplying a first current to the aforementioned capacitor,
a second constant current circuit used for supplying a second current with the opposite polarity to that of the first current to the aforementioned capacitor,
a third constant current circuit used for supplying a third current with the opposite polarity to that of the first current to the aforementioned capacitor,
a first switch element that is electrically connected between the aforementioned capacitor and the first constant current circuit and is turned on corresponding to the aforementioned comparison signal,
a rectifying element that is electrically connected between the aforementioned first switch element and the aforementioned capacitor,
a second switch element that is connected between the aforementioned capacitor and the third constant current circuit, and
a control circuit that uses the aforementioned comparison signal as its input and outputs a control signal for closing the second switch element when the comparison signal does not change during a prescribed amount of time.

6 more elements

Dependencies are inferred from the claim text.