US 5,130,667 A · Differential transimpedance amplifier

Abstract

A wideband transimpedance amplifier utilizing a differential amplifier circuit structure whereby the differential pair is bridged by a signal detector which, as an example, would be a photodetector when the transimpedance amplifier is employed within a optical receiver. In order to bias the signal detector the differential pair is operated asymmetric with respect to the DC voltage but the circuit maintains a symmetric AC response to the signal detector current input. The circuit is designed to operate at the unity gain frequency. The signal detector is placed between the source (or emitter) electrodes of the transistors which helps to reduces the impact of gate (or base) capacitance on circuit response speed. These factors combined maximize the bandwidth capabilities of circuit. The circuit is responsive to a current input to produce two voltage outputs equal in magnitude but opposite in phase.

Claims14

Dependent claims

A differential transimpedance amplifier circuit comprising:

a first and second power source connecting node;
a first current path between said first and second power source connecting nodes having a first resistor, a first output means, a first transistor, and a first current source means all connected in series, and being connected in parallel to a second current path between said first and second power source connecting nodes having a second resistor, a second output means, a second transistor biased differently from said first transistor, and a second current source means all connected in series;
and
a signal detector directly coupled to and connected between said first and second transistors, such that said signal detector is responsive to a received signal inducing an equal in value but opposite in polarity AC response at each of said output means.

1 more element

A differential transimpedance amplifier circuit comprising:

a first and second power source connecting node,
a first circuit comprised of a first resistor, a first output means, and a first transistor, said first transistor having a first electrode, a second electrode, and a third electrode connected to a first biasing means, said first resistor being connected between said first power source connecting node and said first output means and said output means being connected to said first electrode of said first transistor;
a second circuit comprised of a second resistor a second output means, and a second transistor, said second transistor having a first electrode, a second electrode, and a third electrode connected to a second biasing means different from said first biasing means, said second resistor being connected between first power source connecting node and said output means and said output means being connected to said first electrode of said second transistor;
a signal detector means for detecting and converting signal energy to an electrical current directly coupled and connected between said second electrodes of said first and second transistor;
and
a current source means connecting said first circuit and said second circuit to said second power source connecting node.

3 more elements

Dependencies are inferred from the claim text.

Differential transimpedance amplifier

Life of this patent

Differential transimpedance amplifier

Life of this patent

Abstract

Claims14