| 摘要 |
PROBLEM TO BE SOLVED: To stabilize a collector current against the physical fluctuation of environment conditions at the time of performing feedback amplification while compensating the fluctuation of a power supply voltage and to compensate the fluctuation of a frequency band by providing a compensation current source for supplying a current opposing the fluctuation of a voltage and parallelly connecting the compensation current source to a resistor. SOLUTION: A feedback resistor Rf is connected between the emitter side of a final stage output buffer part 2 and the base side of an initial stage amplifier part 1. Also, an environment fluctuation compensation circuit composed of the compensation current source 3 for compensating the reduction of the current and a shunt circuit 4 for shunting the excessive current is provided. Then, the compensation current source 3 is parallelly constituted between the power source Vcc of this preamplifier and the collector side of the initial stage amplifier part 1 and the shunt circuit 4 is parallelly constituted between the emitter side and collector side of the initial stage amplifier part 1 respectively. Thus, the preamplifier of a fluctuation compensation type performs the feedback amplification of an input current while compensating the collector current Ic for the voltage fluctuation of the power source Vcc and ambient temperature change. |
