Rectifier bridge

This invention relates to a complex diode bridge, developed for use in a telephone tone ringer chip, usable, inter alia, in the "chip set" of our Application No. 8317706. The diode bridge is, of course, not so limited in its application. The diode bridge has in each arm a coupled pnp transistor and npn transistor which together act as a diode. Thus in one arm is a pnp transistor (T1) with its collector and base connected together, and an npn transistor (T2) with its emitter and base connected together. The emitter of the pnp transistor is connected to the base of the npn transistor, and the collector of the npn transistor is coupled to the base of the pnp transistor. Two of the npn transistors (T2 and T8) have additional emitters coupled to the substrate to control the voltage level thereof when the bridge input falls below 0 volts.