Abstract: An integrated circuit includes an NPN power transistor and a short-circuit-protection circuit which includes a voltage divider connected directly across the base and emitter of the power transistor. The voltage divider is a series circuit branch having two resistors and a diode connected in the polarity to turn on when the power transistor is on. A smaller NPN transistor has a base-emitter junction connected across a portion of the voltage divider, which portion includes only one of the resistors and the diode. The collector is connected to sink a bias current away from the power transistor when abnormally high currents flow in the power transistor to limit that current to a safe value.

Abstract: An integrated circuit includes a principal photo diode connected to the input of a multistage current mirror amplifier. Darlington cascode circuits are integrated into the output branches of the amplifying stages to obviate nonlinear sensitivity of those stages due to Early effect. Each of the cascode circuits have their input base tied to the top end of a diode string through which a current proportional to the photo current is flowing. Thus, there is no DC component in the two supply terminals; in a dark ambient, no supply/signal current flows; and in a light ambient, the supply/signal current is directly proportional to the light intensity.

Abstract: An integrated circuit photo sensor has a principal photo diode whose reverse voltage is maintained at a low and relatively invariant value by a circuit comprised of a biasing diode string in series with a small auxiliary photo diode and an emitter follower coupling the diode string bias voltage to the principal photo diode. This results in reliable starting without contributing a DC component of current in the power supply so this circuit is suitable for use in a linear two-terminal-type integrated-circuit photo sensor.

Abstract: A current mirror amplifier including three or more tandem stages has a photo diode connected, as usual, with one end at the input of the first stage, but with the other end at the input of a third or later stage, which third or later stage is made up of transistors of the same polarity type (NPN) as make up the first stage. Consequently a very low reverse bias is advantageously applied to the photo diode and the linearity and stability of the resulting photo electric device is enhanced with respect to changing input light levels and with respect to variations in DC supply voltage.