M
Mike Sparrow
Dear all:
I'm desingning a system that sends data through the telephone line.
I'm using an 1N9270 chip (HM9270) tone decoder to identify the DTMF
tones. The valid input signal range level is from 27.5mV to 883mV for
this chip. As the impedance of the line is unknown (aprox. 600ohm),
the amplitud of the receiving signal may be too week if I don't
amplify it enough or too strong if I over amplify it, I don't know how
much attenuation the signal will suffer. That's why I need an AGC. I
used the LM13600 to build the AGC that is described in the datasheet.
It works properly, but the smallest input level signal from which the
AGC works fine is 200 mV and I need to control even smaller level
signal, let's say, 10 mV. By varying the resistors in the design in
the datasheet I got the 200mV. I need that the AGC responds form 10mV
to 5V at the input and at the output from 27.5mv to 883mV. I can't
vary any further (or at least, I don't know how to vary) the value of
the resistors because it causes a distortion at output signal. The
frecuency of my signals are from 600Hz to 2500 Hz.
Has anyone used this Op. Amp. to build an AGC with these or similiar
input signal levels?. Any idea?
Thanks in advance,
Mike Sparrow
I'm desingning a system that sends data through the telephone line.
I'm using an 1N9270 chip (HM9270) tone decoder to identify the DTMF
tones. The valid input signal range level is from 27.5mV to 883mV for
this chip. As the impedance of the line is unknown (aprox. 600ohm),
the amplitud of the receiving signal may be too week if I don't
amplify it enough or too strong if I over amplify it, I don't know how
much attenuation the signal will suffer. That's why I need an AGC. I
used the LM13600 to build the AGC that is described in the datasheet.
It works properly, but the smallest input level signal from which the
AGC works fine is 200 mV and I need to control even smaller level
signal, let's say, 10 mV. By varying the resistors in the design in
the datasheet I got the 200mV. I need that the AGC responds form 10mV
to 5V at the input and at the output from 27.5mv to 883mV. I can't
vary any further (or at least, I don't know how to vary) the value of
the resistors because it causes a distortion at output signal. The
frecuency of my signals are from 600Hz to 2500 Hz.
Has anyone used this Op. Amp. to build an AGC with these or similiar
input signal levels?. Any idea?
Thanks in advance,
Mike Sparrow
