Abstract: A circuit comprises an active filter with linear elements and a tuning circuit with linear elements of the same type as the filter circuit. A backward counter generates a count value that represents a time constant of the tuning circuit. The initial value of the backward counter contains information concerning the relationship between the time constant of the filter circuit and the tuning circuit. A decoder creates a digital code responsive to the count value which is used to switch an array of linear elements in order to tune the time constant of the filter to approximately a desired design value.

Abstract: A comparator comprises a switching means for supplying two different threshold voltages to the comparator upon a first and a second control signal, respectively. The second control signal is enabled by a rising or a falling edge of the comparator output that is coupled to a control means providing the second control signal. The time interval that a varying input signal requires to change its amplitude crossing and in between the two threshold voltages can thus be detected by two subsequent rising or falling edges of the comparator output without the adverse influence of the comparator's meta-stability.

Abstract: A comparator comprises a switching means for supplying two different threshold voltages to the comparator upon a first and a second control signal, respectively. The second control signal is enabled by a rising or a falling edge of the comparator output that is coupled to a control means providing the second control signal. The time interval that a varying input signal requires to change its amplitude crossing and in between the two threshold voltages can thus be detected by two subsequent rising or falling edges of the comparator output without the adverse influence of the comparator's meta-stability.

Abstract: A circuit comprises an active filter with linear elements and a tuning circuit with linear elements of the same type as the filter circuit. A backward counter generates a count value that represents a time constant of the tuning circuit. The initial value of the backward counter contains information concerning the relationship between the time constant of the filter circuit and the tuning circuit. A decoder creates a digital code responsive to the count value which is used to switch an array of linear elements in order to tune the time constant of the filter to approximately a desired design value.

Abstract: A FET square multiplier is disclosed that transforms an input signal into two currents I1 and I2, the difference of which is proportional to the square of the input signal. A first and a second FET are connected at their drains and are source-coupled to the source of a third FET whose transconductance is twice the transconductance of the first and the second FET. The common source node is biased by a constant current source. The FETs are operated in the saturation region to exploit the square dependency of the drain current on the difference of the gate-source voltage and the treshold voltage of an FET.