dramrattan
Member
In the datasheet for the MT8870 there are two configurations in which it can be connected to the TIP and RING lines of a telephone. I want to use the differential input configuration but how do i know what values of capacitors and resistors to use? I know the input capacitors is used to block DC and the resistors form a voltage gain for the amplifier. But again how do i know what values to use? The telephone line is 48V when on-hook, about 90V when ringing and about 10V when dialing or during conversation so do i have to use these values to somehow calculate the capacitor and resistor values to be used?