RFZOFUKUKINIOKERUBAIASUKAIRO

摘要

PURPOSE:To obtain a DC bias circuit for an RF amplifier which performs low- voltage AGC operation with low power consumption by generating a necessary voltage by using a constant voltage element such as a Zener diode. CONSTITUTION:A resistance 18 is set to an about 40OMEGA resistance value and the Zener voltage of the Zener diode 20 is set to about 2V. Resistances 9 and 17 have about 10KOMEGA high resistance and the Zener voltage is impressed to the 1st gate 2 through the resistance 17. A resistance 19 is set almost to 1-4KOMEGA considering that an operating current of about 1-5mA is flowed from a driving source terminal 16 to the Zener diode 20. Consequently, the voltage VG2S between the 2nd gate 3 and source 5 varies between -2-2.4V against 0-5V variation of the AGC signal at a terminal 7 to obtain sufficient gain attenuation.