Abstract: A comparator (10) compares the voltage of a battery (2) with a switchable reference voltage (Uref1A, Uref1B, 18) and supplies a signal (IS) if the voltage of the battery passes the reference voltage. The switching point of the reference voltage is defined by means of a first resistor (32). By means of the first resistor the number of cells of the battery is set to one or two. A second resistor (6) in series with the battery enables an additional voltage to be obtained in order to correct the reference voltage for the type of battery cell used.

Abstract: A capacitive sensor circuit is provided which comprises: a sensor electrode (16) forming a first plate of a sensing capacitor (14) relative to a reference terminal (10), a first (2) and a second (26) inverting Schmitt trigger having the same threshold voltages. A feedback resistor (8) provides feedback from the output (6) to the input (4) of the first trigger (2), which together with the sensing capacitor (14) forms an oscillator whose frequency depends on the magnitude of the sensing capacitor (14). The input (24) of the second trigger (26) is connected to the output of the first trigger (2) via a series resistor (22) and to the reference terminal (10) via a reference capacitor (30). The resistance values of the feedback resistor (8) and the series resistor (22) are equal. A d.c. signal will appear on the output (32) of the second trigger if the capacitance of the sensing capacitor (14) is smaller than the capacitance of the reference capacitor (30) and an a.c. signal in the opposite case.

Abstract: An amplifier circuit, for example, a class AB output stage, includes a series arrangment of a first transistor (T.sub.1) and a second transistor (T.sub.2), both arranged as diodes, a series arrangement of a third transistor (T.sub.3) and a fourth transistor (T.sub.4) and a series arrangement of a fifth transistor (T.sub.5) and an impedance (R). The first main electrode of the first transistor (T.sub.1) is coupled via the impedance (R) to the control electrode of the fourth transistor (T.sub.4). The first main electrodes of the second and fifth transistors (T.sub.2, T.sub.5) are coupled together and to the control electrode of the third transistor (T.sub.3). The control electrodes of the first, second and fifth transistors (T.sub.1, T.sub.2 and T.sub.5) are coupled together and to the second main electrodes of the first and the second transistor. This circuit provides a small quiescent current in the output transistors using relatively small input transistors (T.sub.1, T.sub.