Low distortion driver employing positive feedback for reducing power loss in output impedance that effectively matches the impedance of driven line
First Claim
1. A driver amplifier circuit comprising:
- an operational amplifier having first and second differential polarity inputs and an output;
a first input resistor coupling one of said first and second differential polarity inputs of said operational amplifier to a first reference potential terminal;
a second input resistor coupling another of said first and second differential polarity inputs of said operational amplifier to an input signal terminal to which an input signal is applied;
a negative feedback resistor coupled between said amplifier output and an inverting one of said first and second differential polarity inputs of said operational amplifier;
an output resistor coupled between said amplifier output and an output terminal to which a load being driven is coupled, said output resistor having a resistance Ro that is considerably less than the resistance Rt of said load; and
a further resistor coupled between said output terminal and a non-inverting one of said first and second differential polarity inputs of said operational amplifier;
wherein said driver amplifier circuit has an effective output impedance that is matched to the impedance of said load.
1 Assignment
0 Petitions
Accused Products
Abstract
A line driver with positive feedback reduces the output signal amplitude excursion required for driving a communication line, and enables the driver'"'"'s output impedance to be synthesized using a reduced component value, thereby achieving a reduction in power loss through the output resistor, while simultaneously matching the effective electrical value of the driver'"'"'s output impedance to the line. The line driver includes an operational amplifier having differential polarity inputs and an output. An output resistor, whose value is a fraction of the line impedance, is coupled between the amplifier output and an output node coupled to the line. A negative feedback resistor is coupled between the amplifier output and an inverting input. A further resistor is coupled between the amplifier output and a non-inverting input. The further resistor has a value of k*R, where m=(k+1)/(k-1), R is the value of each of input and negative feedback resistors, and m is the ratio of the desired output resistance Rt to the value Ro of the line driver'"'"'s output resistor.
-
Citations
22 Claims
-
1. A driver amplifier circuit comprising:
-
an operational amplifier having first and second differential polarity inputs and an output; a first input resistor coupling one of said first and second differential polarity inputs of said operational amplifier to a first reference potential terminal; a second input resistor coupling another of said first and second differential polarity inputs of said operational amplifier to an input signal terminal to which an input signal is applied; a negative feedback resistor coupled between said amplifier output and an inverting one of said first and second differential polarity inputs of said operational amplifier; an output resistor coupled between said amplifier output and an output terminal to which a load being driven is coupled, said output resistor having a resistance Ro that is considerably less than the resistance Rt of said load; and a further resistor coupled between said output terminal and a non-inverting one of said first and second differential polarity inputs of said operational amplifier; wherein said driver amplifier circuit has an effective output impedance that is matched to the impedance of said load. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
-
-
13. A driver amplifier circuit comprising:
-
a first operational amplifier having first and second differential polarity inputs and an output, said first input of said first operational amplifier being coupled through a first input resistor to an input signal terminal to which an input signal is applied, and said second input of said first operational amplifier being coupled to a reference potential terminal, a negative feedback resistor coupled between an amplifier output and said first input of said first operational amplifier, and an output resistor coupled between said amplifier output and an output terminal to which a load being driven is coupled; and a second operational amplifier having first and second differential polarity inputs and an output, said first input of said second operational amplifier being coupled through a first input resistor to said output terminal to which said load being driven is coupled, said second input of said second operational amplifier being coupled to a reference potential terminal, a negative feedback resistor coupled between an amplifier output and said first input of said second operational amplifier, and an output resistor coupled between said second operational amplifier output and said first input of said first operational amplifier, so as to form a positive feedback path between said output of said first operational amplifier and said first input of said first operational amplifier. - View Dependent Claims (14)
-
-
15. A line driver comprising an operational amplifier having differential polarity inputs and an output, an output resistor whose value Ro is less than and only a fraction of a resistance Rt presented by said line, coupled between the operational amplifier output and an output node that is coupled to said line, a negative feedback resistor having a value R coupled between the operational amplifier output and an inverting input thereof, and a further resistor coupled between said output node and a non-inverting input of said operational amplifier, and wherein said further resistor has a value of k*R, where (k+1)/(k-1)=m, m being the ratio of Rt to Ro, and wherein said line driver has an effective output impedance that is matched to the impedance of said line.
-
16. A method of driving a communication link with a signal to be transported thereover comprising the steps of:
-
(a) coupling said signal to an operational amplifier; (b) coupling an output of said operational amplifier through an electrical circuit element to said communication link, said electrical circuit element having an impedance less than that of a load impedance presented by said communication link to said output of said operational amplifier; and (c) causing the effective electrical impedance of said operational amplifier at the coupling of said electrical circuit element with said load to match said load impedance presented by said communication link, by providing positive feedback between the communication link side of said electrical circuit element and an input of said operational amplifier. - View Dependent Claims (17, 18, 19, 20, 21, 22)
-
Specification