| 摘要 |
PURPOSE:To reduce distortion by providing a negative feedback circuit in the separation circuit for left and right channel signals in a FM stereophonic receiver. CONSTITUTION:When switching signal e2 is in the positive half cycle, the upper- stage differential part of double balanced amplifier DBA11 is constituted. TrQ13, Q14, Q20 and Q21 are turned on, and TrQ15, Q16, Q18 and Q19 are turned off. Consequently, the current flows to load resistance R2 through TrQ13, and the output of the left channel is separated and is led out to LOUT. At this time, the signal current is fed back to the emitter of TrQ11, which constitutes pre-amplifier A11, through TrQ14, and the bias current is fed back to the emitter of TrQ22 through TrQ20. When switching signal e2 is in the negative half cycle, the operation of Tr is reverse to the operation above, and the output of the right channel is led out to terminal ROUT. |
