question about coupling & impedance matching

[tabooes]

Hi everyone!!!
I am new to electronics, I got a question as below.

As the attached sch shows, the 128k and 64k input signal was connected with a resistor and capacitor, then a potentiometer. What do they do?

I think they just match the impedance with the IC mc4053.

Thank you very much for your opinions!!!

[AndrewT]

Hi,
is the 128K and 64K the bit rate?

I would expect to see 128kb or 128kb/s.

C100 & C103 look like a DC block from either direction.
R100 & R101 could be stability loading.

[tabooes]

the 128k and 64k mean the input signal: 128kHz and 64kHz square or sine wave or else.

what does your "stability loading" mean? could you tell me more or give me a related web?

thank u :-)

[AndrewT]

Hi,
some opamps don't like capacitance on their outputs.
A little resistance isolates the capacitance and maintains the phase margin.

Have a look at WJung's site for lots of very detailed and absolutely accurate info on opamps.
www.waltjung.org look at library/ classic for a listing

It might be here.
http://waltjung.org/PDFs/ADI_2002_Se..._Drivers_I.pdf