| 摘要 |
PROBLEM TO BE SOLVED: To provide an AGC amplifier circuit capable of obtaining a maximum gain and the simplifying the configuration of an external gain control circuit by expanding the effective range of a gain control voltage VAGC so as to eliminate an existent limit. SOLUTION: In a current distributing type AGC amplifier circuit, plural pairs of GaAs, MESFET J3, J4 and J8, J9 for varying gains are parallelly connected to apply gate voltages different from each pair of these FET J3 J4, J8 and J9 for varying gains based on the gain control voltage VAGC to prevent undesired gain deterioration in a gain control voltage range larger than conventional one. A diode D1 is connected between the respective gate terminals of FET J3, J4 and J8, J9 for varying gains connected in parallel, and FET J11 to be a constant current source is connected to the diode to allow a constant current to flow to apply the different gate voltages for each pair of FET J3, J4 and J8, J9 for varying gains. |
