be substantially the same it has been found that circuits can be manufactured where transistors 15 will have a breakdown of 65 volts whereas transistors 12 and 13 break down at 75 volts clearly whatever the voltage breakdown for transistors 12 and 13 transistor 15 will be lower by virtue of physical design and the fact that all three devices are fabricated simultaneously in adjacent silicon areas thus the desired characteristics are self tracking because of the process also because of the proximity any thermal effects will tend to act equally on all three devices which will therefore tend to track diffusion 30 represents a collector contact diffusion this provides an ohmic low resistance connection via buried layer 21 to the collector regions of all three transistors since the collectors are all connected together region 30 is a single continuous diffusion region surrounding the three transistors while not shown the silicon surface is coated with the conventional planar oxide and a metalization layer that makes contact through holes etched in the oxide to the diffused emitter base and collector electrodes the metal is contoured so that emitters 28 are parallel connected by means of a series of eight fingers base metal contact fingers interdigitate the emitter metal contacts and connect to parallel connected emitters 29 as well as to emitter 27 a metal base finger paralleling emitters 29 would comprise the circuit input terminal 8 resistor 15 could be in the form of the resistive metalization or.