| 摘要 |
PURPOSE:To achive stable operation, by inserting a series connection circuit of a low-pass filter and a terminating resistor between a line coupling a high frequency power amplifier and an isolator, and ground. CONSTITUTION:In a high frequency power amplifier 1, a combination circuit between a low-pass filter 3 and a termination resistor 4 is inserted between the output terminal and an input terminal of a lumped constant cirdulator type isolator 2. Further, one end of the resistor 4 is grounded. Thus, by selecting the cut-off frequency of the low-pass filter between f0 and f0/2, although the input impedance of the isolator 2 is almost opened at low frequencies of outside of the required band, the resistor 4 connected to the filter 3 can be existed at frequencies below f0/2 without any effect to the characteristics of the isolator 2 essentially. Thus, the instability of the amplifier 1 can be eliminated through the selection of the value of the resistor 4. |
