US 4,053,797 A · Receive amplifier for PAM signals

Abstract

A decoded PAM input signal is coupled through a first polarity switch (which for one polarity of a polarity signal is closed) to the positive input line of a differential operational amplifier and through the series combination of a second polarity switch (which is open for the one polarity) and an input resistor to the negative input line of the differential amplifier. The positive input line is resistively connected to ground through a first bias resistor and is also connected to ground through the series combination of a second bias resistor and a third polarity switch which is also open for the one polarity. A feedback resistor is connected between the output line and the negative input line of the amplifier. By proper selection of resistances, this circuit provides a prescribed amplification of an input signal and changes its polarity as a function of a digital polarity signal that is applied to the switches, the circuit providing no change in output signal for a change in polarity signal when the input signal is of zero amplitude.

Claims12

Dependent claims

Apparatus for converting an input train of amplitude-varying pulses of one polarity to an output pulse train having a polarity as a function of a polarity signal which is associated with the input pulse train and has first and second amplitude levels corresponding to one and other polarities of output pulses, comprising:

first and second reference points;
first, second, third, and fourth resistors;
first, second, and third switch means;
a differential-input operational amplifier having a first input terminal connected through said first switch means to said first reference point, connected through said first resistor to said second reference point, and connected through the series combination of said second resistor and said second switch means to said second point, and having a second input terminal electrically connected through the series combination of said third resistor, which is an input resistor, and said third switch means to said first point and connected through said fourth resistor, which is a feedback resistor, to an output terminal of said amplifier;
and
control means responsive to the polarity signal for closing said first switch means and opening said second and third switch means in response to a polarity signal of the first level, and for opening said first switch means and closing said second and third switch means in response to a polarity signal of the second level.

3 more elements

A circuit responsive to input signals which are decoded PAM pulses of only one polarity and an associated polarity signal which has first and second amplitude levels corresponding to first and second polarities of reproduced sampled PAM pulses of both positive and negative polarities in the circuit output signal whose amplitude remains substantially unchanged where the polarity signal changes amplitude during receipt of a plurality of input PAM pulses of zero amplitude, comprising:

a differential-input amplifier having first and second input lines and at least one output line;
first switch means electrically connected in series between said first input line and a first reference point;
a first resistor electrically connected in series between said first line and a second reference point;
a second resistor and second switch means electrically connected in series between said first line and said second point;
a third resistor and third switch means electrically connected in series between said second input line and said first point;
a fourth resistor, which is a feedback resistor, electrically connected between said second input line and an output line of said amplifier;
and
control means responsive to the polarity signal for closing said first switch means and opening said second and third switch means in response to a polarity signal of the first level, and opening said first switch means and closing said second and third switch means in response to a polarity signal of the second level.

5 more elements

Dependencies are inferred from the claim text.

Receive amplifier for PAM signals

Life of this patent

Receive amplifier for PAM signals

Life of this patent

Abstract

Claims12