Title: Integrated circuit for class-B power amplifier

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Abstract: A Class-B power amplifier, designed as a monolithically integrated circuit, comprises in its final stage an NPN output transistor Q4 whose base is driven by an NPN control transistor Q3 through the intermediary of a pair of current-replicating PNP transistors Q6, Q7 with interconnected bases having their emitters tied to the collector of the output transistor. Their common base lead, also tied to the collector of the replicating transistor Q6 to connect same as a diode, is joined to the collector of control transistor Q3; the collector of the second replicating transistor Q7 is joined to base of the output transistor Q4. An alternating signal is fed to the base of a PNP input transistor Q1 lying in series with a NPN pilot transistor Q2, the collectors of the two latter transistors being tied to the base of the control transistor Q3 whose emitter is connected to a load terminal jointly with the emitter of the output transistor Q4. On negative half-cycles of the signal to be amplified, the second replicating transistor Q7 saturates before the input transistor Q1 to maximize the output voltage on the load terminal.


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