| 摘要 |
<p>PURPOSE:To perform high-precision envelope waveform shaping by increasing the gain of a variable gain amplifier and thus performing optimum envelope detection. CONSTITUTION:A synchronizing information signal arrives at an input terminal 5 and a synchronizing signal generating circuit 6 extracts and outputs a synchronizing signal to a ramp function generating circuit 9. The circuit 9 generates and outputs a synchronizing ramp waveform which corresponds to the synchronizing signal inputted to the circuit 6. This output is inputted to the gain control terminal 13 of a variable gain amplifier 12 to vary the gain of the amplifier. Namely, the gain is in proportion to the ramp waveform; the gain is maximized when a synchronizing pulse rises and increases until the next synchronizing pulse is generated. Consequently, variation in intermediate point during envelope detection is lessened to perform the detection at the best detection position invariably.</p> |
