Power amplifier circuit
AssigneeNippon Gakki Seizo Kabushiki Kaisha
InventorKenro Oguri
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Abstract
A power amplifier circuit comprising a voltage amplifier stage and a current amplifier stage, the mode of bias of which can be changed over between class A and class B (AB). The supply voltage for the current amplifier stage is changed over by a mode selection switch. The change in the supply voltage is detected to select the bias voltage for the current amplifier stage. The possibility of applying a class A bias to the current amplifier stage supplied with a class B line voltage is thus completely removed.
Claims6
In a dual operational mode power amplifier of the type comprising a voltage amplifier, a current amplifier receptive at an input port of signals from said voltage amplifier, and change over means for selectively changing the voltage supply level and bias condition of said current amplifier to establish thereby the operational mode of said power amplifier, the improvement wherein said change over means comprises:
- means for detecting the level of said current amplifier supply voltage level and generating a signal in accordance with the relative magnitude of said supply voltage level and a reference level;
- and
- means responsive to said detecting means signal for establishing said current amplifier bias condition, such that changes in said biasing are effected only when said supply voltage level is in predetermined relation to said reference level, whereby excess currents in said current amplifier are avoided.
Dependencies are inferred from the claim text.