I am trying to build some kind of telephone interface. My circuit should act as telephone central, so it must give power supply to connected phone. Also 2wire/4wire decoding is needed. I found suitable schematics - you can see it there:
But in this circuit there are two coils (L2 L3) which separates direct current from signal, 210 mH each (to big size for me). I am searching for any solution to replace this coils with something else.
Is it possible? Maybe some kind of 'dummy inductance' or current source realized with opamp driwing power transistor?
Thanks for any help.
For those who dont want to download PDF from link given above there is schematics of interested part of circuit.
- 50V | | L2 | +-----------C---- | o To phone rest o of | circuit +-----------C---- | L3 | | ----- --- -