U.S. Philips Corporation

Werner F Thommen

Arpad Korom

Werner Fehr

A delay-controlled relaxation oscillator includes a capacitance in the oscillator which is alternately charged and discharged. The change-over from charging to discharging is controlled by means of a comparator which compares the capacitance voltage with a reference voltage. The oscillator also includes switching means for reducing the power consumed by switching the power supply for the comparator from the power supply mode into a stand-by mode between two change-overs.

Delay-controlled relaxation oscillator with reduced power consumption

An oscillator, for example, a ring oscillator, comprises an oscillator stage which includes a current source in series with a parallel connection of a switching element (a transistor) and a capacitance. A delay circuit is connected between the junction point of the current source and the parallel connection and the input of the switching element. The oscillation frequency is determined to a suitable approximation by the capacitance and by the ratio of the magnitude of the switching threshold of the switching element and the current to be supplied by the current source. A frequency stabilization means for the oscillator adjusts the current to be delivered by the current source by means of a resistor so that the ratio of this current and the switching threshold is proportional to the value of the resistor. The constant resistance value of the resistor is then a factor which determines the oscillation frequency.

Frequency stabilized oscillator

A sample-and-hold circuit arrangement comprising a differential amplifier (5) followed by an inverting amplifier (8). A third amplifier (12) is provided having a capacitor (14) which connects an output of the third amplifier to its input. The inverting amplifier ensures that the voltage on the output (16) of the arrangement is independent of the offset voltage of the differential amplifier (5). Moreover, during a sampling interval the capacitor (14) maintains the voltage on the output (16) at the value which it had in the directly preceding hold interval.

Sample-and-hold circuit arrangement

The invention relates to a sample-and-hold circuit arrangement comprising a differential amplifier (5) followed by an inverting amplifier (8). In accordance with the invention there is provided a third amplifier (12) and a capacitor (14) which connects an output of the third amplifier to its input. The inverting amplifier (8) ensures that the voltage on the output (16) of the arrangement is independent of the offset voltage of the differential amplifier (5). Moreover, the capacitor (14) maintains the voltage on the output (16) during a sampling interval at the value which it had in the directly preceding hold interval.

A stepping motor (M) with a self-inductance L is energized with pulses. If the motor current i.sub.m is less than a reference value I.sub.R =V.sub.ref /R.sub.o, the motor is connected to the battery and if i.sub.m is greater than I.sub.R the motor is short-circuited. The motor current therefore fluctuates around the value I.sub.R. The motor current is adjusted so that the average voltage during a first measuring interval, in the range of the maximum angular velocity, is twice that during a second measuring interval at the end of the energizing phase. The two average voltages are compared with each other by measuring the time during which the switch (S) is in the energizing position. In this way it is not necessary to measure the voltage induced in the self-inductance L and every motor pulse is checked constantly. The motor current is adjusted at the end of the energizing phase to provide a correct adaptation to the required motor torque. Tolerances of all the elements involved, including the motor, are automatically compensated.

Method of and circuit arrangement for controlling the torque of a

In order to enable two different internal circuits to be controlled from one input pin of a C-MOS IC said pin is connected directly to an input of a first circuit and via the emitter-collector path of a transistor to the input of a second circuit. The base of this transistor is connected to one of the supply voltages, so that this transistor can conduct only when the voltage on said input pin is higher or lower than the positive or negative supply voltage respectively.

Integrated circuit having first and second internal circuits controlled

A push-pull amplifier consisting of a complementary pair of output transistors whose bases are interconnected by a resistor. According to the invention, the bases are separately connected to the outputs of two current mirrors whose inputs are interconnected via a second resistor. A relation is then obtained between the values of the two resistors for which the quiescent current through the output transistors is supply-voltage independent in a first-order approximation.

Push-pull amplifier

A current source circuit degeneratively feeds back a control signal to a current mirror circuit via a single stage amplifier in order to reduce instabilities resulting from use of more than one stage.

Growing community of inventors

Staefa, Switzerland

Werner F Thommen