PURPOSE: To obtain an output signal in phase with an input with a simple constitution, by inputting the input signal to a negative input terminal of an integrator via a switched capacitor.
CONSTITUTION: The relation between a switched capacitor and a resistor is expressed as K4CB=T/R4 and K2CB=T/R2 (where T is the sampling period). That is, the resistor R4 correspons to the K4CB and the resistor R2 corresponds to the K2CB. An input signal is divided by resistors Ra, Rb and inputted to a positive input terminal of an operational amplifier 5. Further, a part of the same input signal is inputted to a inverting input terminal of the operational amplifier 5. Equation 5 (where S=jω) is obtained by obtaining an output voltage V2. The principle of this invention is that the 6th term (integration) is cancelled by the 4th term to obtain the 5th term of inphase output which is a multiple of input voltage inputted from a noninverting input terminal of the operational amplifier. The integration or a multiple of the inputted voltage from the inverting input terminal of the operational amplifier 5 is the same as conventional value.
UENO NORIO
TSUNOISHI MITSUO
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