| 摘要 |
PURPOSE:To switch and set the intermediate frequency pass band width for broad and narrow band and to reduce the number of components, by constituting the 1st and 2nd resonance circuits with the 1st and 2nd IF transistors, the 3rd resonance circuit and switching means. CONSTITUTION:The resonance circuit T1 of the 1st IF transformer IF1 is connected to the collector side of a transistor TR1 as a load. The secondary winding L1 or IF1 is connected to the primary winding L2 of the 2nd IF transformer IF2, and accordingly a closed circuit with the secondary winding L1 of IF1, resonance circuit T2 and the primary winding L2 of IF2 is formed. Further, the intermediate tap of the secondary winding constituting the resonance circuit T3 provided with the secondary side of IF2 is connected to a detection circuit, not shown, via the output terminal OUT. On the other hand, the resonance circuit T2 is formed with a by- pass conduction path BP by-passing it, and this conduction path BP is provided with a transistor TR2 which is on/off according to the switching of this switch SW. |
