| 摘要 |
PURPOSE:To cope with a wide input signal level range and a frequency range by applying positive feedback to limit an output current supply of a main differential amplifier under the unity gain in response to the output current of a sub-differential amplifier. CONSTITUTION:The current flowing to transistors (TRs) Q15, Q16 of the sub- differential amplifier B is controlled by a collector output of TRs Q11, Q12 of a main differential amplifier A. Then the current flowing to the TRs Q13, Q14 of the amplifier A is controlled in response to a voltage generated between the base and emitter of the TRs Q15, Q16, emitter resistors (R) 15, 16 and resistors R13, R14 to form a feedback loop to apply positive feedback only around the center of the output amplitude range with respect to the amplifier A. The loop gain is set to the unity or lower. Thus, the circuit copes with a wide input signal level range and frequency range. |
