Abstract: A low supply voltage for operating an operational amplifier operating as a voltage follower is derived from a high voltage source. Two npn transistors, two Zener diodes and a current source are connected in series across the high voltage source. The input voltage (to the operational amplifier) plus a Zener reference voltage is applied to the base of the transistor near the positive terminal of the high voltage source. Then, a low positive supply voltage V+ nearly equal to the input voltage plus the Zener voltage (Vi+Vz) is derived at the emitter. This low positive supply voltage V− is derived by dropping V+ through the two series Zener diodes to obtain a low negative supply voltage equal to (Vi−Vz).

Abstract: A surface-mounted flat package for a laser diode has the laser diode and light sensor diode mounted on top of a printed wiring insulating substrate. These diodes are connected to electrodes at the corners of the package. These electrodes may be fed through plated through via holes to form bottom electrodes. These via holes may be located at the four corners of the substrate or inside the edges of the package.For mass production, a matrix of laser diode and sensor diode assemblies are mounted on a common substrate. The substrate is sawed orthogonally through or outside the via holes to yield a large number of dice.