| 摘要 |
<p>Amplifier arrangement. A high efficiency amplifier of the class-G type comprises a first transistor (T1) whose collector is connecconnected to a first supply voltage (V1) via a first diode (D1), and a second transistor (T2) which is connected in series with said first transistor and which has its collector connected to a second supply voltage (V2). The first transistor (T1) is driven via a third transistor (T3), which is connected as an emitter follower by means of a first current source (5), to which third transistor the input voltage (Vi) is applied. For a low input voltage (Vi) the second transistor (T2) is cut off and the first transistor (T1) is connected to the first supply voltage (V1) via the first diode (D1) Above a specific input voltage (Vi) the second transistor (T2) is driven into conduction by a driver circuit, so that the first transistor (T1) is connected to the second supply voltage (V2). This driver circuit comprises a current path which is arranged between the second supply voltage (V2) and a common terminal ( 11 ) and which comprises the series arrangement of a first current source (7), a second and a third diode (D2 and D3), and a second current source (8). The junction point (3) between the first transistor and the second transistor (T1, T2) is connected to the anode (9) of the second diode (D2) by means of a third diode (D4) and the emitter of the -third transistor (T3) is connected to the second current source (8) by means of a fifth diode (D5). By means of such a driver circuit the output (2) can be driven to a voltage which is equal to the second supply voltage (V2) minus substantially one base-emitter voltage. Fig. 1.</p> |
