Abstract: There is provided a light-receiving and amplifying device capable of changing its gain at high speed. A cathode of a photodiode PD is connected to a power source V.sub.CC via a current mirror circuit. An anode of the photodiode PD is connected to an input of an amplifier circuit AMP. The amplifier circuit AMP receives a photocurrent from the photodiode PD, converts the photocurrent into a voltage, and amplifies the voltage to form an output signal V.sub.OUT. A control signal of a current having the same magnitude as that of the photocurrent and output from the current mirror circuit is input to a control input terminal of a gain switching circuit. The gain switching circuit is composed of a resistor Rf.sub.1, a resistor Rf.sub.2, and a switch SW. The resistor Rf.sub.1 is connected across the input and the output of the amplifier circuit AMP, and the resistor Rf.sub.2 and the switch SW connected in series are connected across the input and the output of the amplifier circuit AMP.

Abstract: A light-receiving and amplifying device includes a plurality of photodiodes and amplifier circuits which receive inputs from anodes of the photodiodes. There is provided a first current mirror circuit for outputting a second current having the same magnitude as that of a first current which is a sum of currents flowing through cathodes of the photodiodes. Further provided is a second current mirror circuit which receives the second current from the first current mirror circuit and receives divided currents each having an even magnitude from the anodes of the photodiodes. An AC operation range of the light-receiving and amplifying device is widened in a simple manner at a low cost without significant dimensional increase of the device.

Abstract: A waveform converting apparatus includes a first and a second common-emitter type transistors as part of a first and second emitter follower circuits respectively. The follower circuits are used for converting the impedances of an input signal independently. A first constant current supply is connected to the emitter of the first transistor provided in the first emitter follower circuit, and a second constant current supply is connected to the emitter of the second transistor provided in the second emitter follower circuit. The constant current flowing in the first emitter follower circuit is adjusted to be of a smaller value than the constant current flowing in the second emitter follower circuit.

Abstract: An alphanumeric visual display of the matrix type for use in electronic digital wristwatches and similar devices is adapted to display relatively lengthy numerical or character information on a relatively short display area through a consistently varying display fashion. More specifically, display operation takes place in such a manner as to increase an enabled or disabled region (as defined by the number of columns enabled or disabled, respectively) progressively with the passage of time through the utilization of a train of sequentially phase shifted gate signals.