NONLINEAR AMPLIFYING CIRCUIT

摘要

PURPOSE:To obtain a small gain for a low input signal and a large gain for high input signal, by controlling the amount of negative feedback with a nonlinear switching element. CONSTITUTION:Transistors(TRs) Q3, Q4 constitute a differential amplifying circuit and TRs Q1, Q2 form a current mirror circuit. A TRQ5 forms an emitter follower circuit. With the absence of input signals, voltages V1, V2 are set to turn off TRs Q6, Q7. When a signal of input level for the AC level of VBQ4 which satisfies V1+VBEQ7>VBO4>V2-VBEQ6 is inputted, the TRs Q6, Q7 turn off. Next, the signal of input level in which the AC level of the VBQ4 satisfies V1+ VBEQ7VBQ4 is inputted, the TRQ7 turns on and one end of a resistor R3 is grounded as AC. Thus, in this amplifier, a small gain can be obtained for a low input signal and a high gain to a high input signal, respectively.