| 摘要 |
<p>A servo circuit adapted for controlling a variable gain amplifier to process an audio signal in a television receiver, a stereo apparatus or the like. The servo circuit comprises a variable gain amplifier (140) so formed that the gain thereof is variable with a predetermined temperature coefficient to an absolute temperature, an amplitude limiter (46) for setting upper (48) and lower (49) limits of the gain variable range of the amplifier (140), a gain control range determiner for changing the upper and lower limits of the gain variable range in the amplitude limiter with a temperature coefficient inverse in polarity to that of the amplifier, and a signal processor for detecting and calculating the level of a control signal supplied to one input terminal and the level of a process signal supplied to the other input terminal, and then outputting a gain control signal in accordance with the level difference between the two input signals so as to control the gain of the variable gain amplifier (140). When the servo circuit is formed into an IC configuration, a high-precision operating characteristic is attained merely by a bipolar-transistor manufacturing process to consequently minimize the number of required process steps, hence curtailing the production cost. <IMAGE></p> |
