A frequency-shaping network is disclosed which combines voltage-controlled voltage sources and current-controlled current sources to provide a voltage integrator. By combining the controlled sources to form an integrator, advantageous use may be made of this integrator in a frequency-shaping network in order to provide a transfer function which is relatively insensitive to the gain of the amplifiers used in the controlled sources. Further, the transfer function coefficients may be relatively independently and easily determined by merely choosing desired impedance values.
Circuitry for filtering a distinct variable spectral component includes a band-rejection filter formed by a summing amplifier with a feedback loop and a bandpass-filter connected to one of its inputs. The summing amplifier is connected to form the difference between the unfiltered spectrum at one of its inputs and the spectrum component to be suppressed at another of its inputs. The summing amplifier delivers the filtered signal spectrum at its output. A control circuit locks the common center frequency of the bandpass and band-rejection filters to the frequency of the spectral component to be suppressed.
A hand off integrator apparatus utilizing first and second recirculating integrator units in series to integrate a series of input pulses in order to detect the presence of weak signals in a high background noise environment.
To provide a fully differential sampling circuit which reduces a sampling error to suppress the occurrence of a second harmonic component. The sampling error is resulted from voltage dependence of a capacitance of the capacitor formed on a semiconductor substrate. The present invention includes a first sampling capacitor 27, a second sampling capacitor 28, four switches 31, 32, 33', and 34 for charging and discharging the first sampling capacitor 27, four switches 41, 42, 43', and 44 for charging and discharging the second sampling capacitor 28, and a fully differential operational amplifier 20 including a first integral capacitor 25 and a second sampling capacitor 26. An upper layer electrode 28b and a lower layer electrode 28a of the second sampling capacitor 28 are opposite to the first sampling capacitor 27 in connecting direction (state).
