High efficiency amplifier having a bootstrap capacitor

摘要

A high-efficiency class-G type amplifier comprises a first transistor (T1), having its collector connected to a first supply voltage (V1) via a first diode (D1) and a second transistor (T2), connected in series with the first transistor and which has its collector connected to a second supply voltage (V2). The series arrangement of a second (D2), a third (D3) and a fourth diode (D4) is connected between the bases of the first and the second transistor (T1, T2) the fourth diode (D4) is poled in a direction opposite to that of the second (D2) and the third diode (D3). The series arrangement of a first resistor (R1) and the emitter-collector path of a first current-source transistor (T4) connects the second supply voltage to the anode of the fourth diode (D4). The junction point (5) between the first resistor (R1) and the current-source transistor (T4) is connected to the output (2) by means of a capacitor (C1). This arrangment drives the output to a voltage substantially equal to the second supply voltage (V2).