| 摘要 |
<p>The circuit suppresses a very narrow frequency band from a wide band spectrum by means of a drain circuit using a quartz with an active element switched in front. One pole of the quartz (Q) is connected to the transmission lead, while the other pole is connected to one side of a trimming condenser (C1) leading to earth. An integrated operational amplifier (OP) follows the quartz (Q) so that the transmission lead is connected to the non-inverted input. The junction of two resistors (R3, R4) is connected to the inverted input. One resistor (R3) leads to earth while the other (R4) is coupled to the amplifier's (OP) output terminal. Another trimmer (C2) bridges this terminal and the non-inverted input.</p> |
