IF amplifier design

Discussion in 'Wireless & RF Design' started by froten_140, Aug 23, 2010.

  1. froten_140

    Thread Starter Active Member

    Jun 4, 2006
    Hello All,
    I'm trying to build a multistage (3 stages) 455KHz IF amplifier. The circuit is a common emitter with primary tuned transformer on the collector. I can not get IF transformers so I have to build them by my self. I have a big problem to design the transformer as follows:
    1) What L & C should I use for the primary side for 455KHz?
    2) What L should I use for the secandary side?if the next stage input impedance is 3.3K for example.
    3) What is the turns ratio should I use? if the next stage input impedance is 3.3K for example.
    I realy have seriose problem with selection of L&C and N. Any help is greatly appreciated.
  2. skeptic

    Active Member

    Mar 7, 2010
    I wouldn't use an interstage transformer. I would use a fixed coil from collector to Vcc. From the junction of the collector and the coil I'd put a series capacitor to the input of the next stage. Also from the input of the next stage I'd put a capacitor to either Vcc or ground.

    You must select the values of the coil and capacitors to not only make the network resonate at 455 kHz but also do impedance transformation between the two stages.
  3. bertus


    Apr 5, 2008