| 摘要 |
A radio transmitter 100 comprises a microphone 110, a low- frequency amplifier 120, a splatter filter 130, a potentiometer 140, a modulator 150, an oscillator and transmission circuit 180 and an antenna 190. The low-frequency amplifier 120 comprises an operations amplifier 160 with an input resistance 162 which is connected to the microphone 110 via a condenser 168, a phase difference filter 170 which is connected to the output of the operations amplifier 160, and a feedback resistance 161 which is arranged between the filter 170 and the input resistance 162. When the amplifier is operated for clipping, the phase and amplitude of harmonic signals from the operations amplifier 160 of the phase difference filter 170 are changed, whereby excess oscillation in the modulation signal is avoided. During linear operation the low-frequency amplifier 120 has flat characteristics, so that the filter 170 has no effect, as it is arranged in the feedback connection loop. The circuit can advantageously be used in both AM and FM transmitters to improve the signal quality of the transmitter. <IMAGE> |
