| 摘要 |
<p>The object of the circuit modification is to simplify the construction of the power amplifier. To achieve this the preamplifier (1), producing a pulse modulated output corresponding to the input signal (E), is coupled to the power amplifier driver (3) through an opto-coupler (2). Using light transmission the input signal to the driver amplifier is galvanically isolated from the preamplifier. This isolation permits the use of a simple power supply comprising a rectifier (4) and smoothing capacitor (C2) directly connected to the ac mains without a transformer. The rectifier can produce an effective voltage of 100V on the loudspeaker circuit from a 220V mains supply. With the employment of complementary FETs (T1,T2) the arrangement enables high power output. It is helpful if VMOS FETs are employed.</p> |
