Semiconductor charge devices are defined to effect a serial-to-parallel conversion of analogue signal information. In one aspect of the invention, a digital signal is extracted from an analogue noise environment by a shift register correlator comprising a bucket-bridge configuration of field-effect transistors in combination with gating field-effect transistors which are effective to weight the amplitude of the data in corresponding bits of the shift register. The gates of the gating transistors are selectively connected to diffused regions of transistors of the bucket-brigade delay line to effect parallel tapped outputs therefrom. The weighted signals from the gating transistors are summed at a common terminal to form the auto-correlated output. In a different aspect of the invention, the analogue delay line is effected by a charge-coupled shift register, parallel taps being obtained from diffused regions under selected electrodes of the shift register ohmically connected to gates of the gating field-effect transistors.
The capacitance of a compensating reverse biased diode is added to the capacitance of a pn junction formed by surface depletion and inversion in a charge coupled device having variations in depletion capacitance which are to be compensated. Because the compensating diode is connected in an opposite sense with respect to the pn junction, an increase in small signal variations in the potential across the pn junction causes a decrease in small signal variations in the potential across the compensating diode. The resulting change in the capacitance of the pn junction is accompanied by a corresponding opposite change in the capacitance of the compensating diode so that the combined capacitance of the two elements remains nearly constant during all small signal variations in potential.
A method and an apparatus for selectively summing the time-varying components of a plurality of electrical voltages are disclosed. The electrical voltages can each be characterized by a quiescent bias component and a time-varying small signal information component. Each electrical voltage is selectively connected to at most one of a plurality of summing buses and each bus is allowed to separately float to a quiescent voltage level corresponding approximately to a selected average value of the bias components of the signals connected thereto. The potential difference measured between the buses corresponds to the difference in the weighted average values of the time-varying components connected to each bus. The weights may be equal or unequal. The method and apparatus provide means for implementing programmable transversal filters and correlation devices.
