Variable gain amplifier with temperature compensation and gain linearity enhancement
AssigneeLinear Technology Corporation
InventorMin Z. Zou
Life of this patent
Estimating the term…
Abstract
A variable gain amplifier contains a plurality of differential transistor pairs. A temperature dependent current is generated in the current path of each differential transistor pair. A generated gain control current is converted to a temperature dependent gain control current and applied in circuit with control inputs of the transistors of the paired differential transistors. The temperature dependent gain control current is obtained from a gain control current corresponding to a desired gain which is then multiplying the control current by the temperature dependent current. The temperature dependent gain control current is modified to compensate for gain non-linearity by introducing an offset as a function of the gain control current.
Claims8
A variable gain amplifier comprising:
- a plurality of differential transistor pairs coupled in parallel, wherein
- each transistor pair is coupled to a temperature dependent current source,
- control inputs of the transistor pairs are coupled to a temperature dependent gain control signal, and
- a temperature compensation circuit configured to generate the temperature dependent gain control signal, the temperature compensation circuit comprising:
- a first transistor having a control terminal coupled to a control current source and to a zero temperature coefficient source and an output terminal coupled to current source proportional to temperature;
- and
- a second transistor having an output terminal coupled to the current source proportional to temperature;
- wherein the conduction current of the second transistor is applied as the temperature dependent gain control signal.
A method of controlling a variable gain amplifier composed of a plurality of parallel coupled differential transistor pairs, the method comprising:
- producing a temperature dependent current source in the current path of each differential transistor pair;
- generating a gain control current corresponding to a desired gain;
- converting the generated control current to a temperature dependent gain control current and
- applying the temperature dependent gain control current source in circuit with control inputs of the transistors of the paired differential transistors;
- and
- modifying the temperature dependent gain control current source to compensate for gain non-linearity.
A method of controlling a variable gain amplifier composed of a plurality of parallel coupled differential transistor pairs, the method comprising:
- producing a temperature dependent current source in the current path of each differential transistor pair;
- generating a gain control current corresponding to a desired gain;
- converting the generated control current to a temperature dependent gain control current source;
- applying the temperature dependent gain control current source in circuit with control inputs of the transistors of the paired differential transistors;
- wherein the step of converting comprises;
- generating a temperature dependent current source;
- and
- multiplying the control current by the temperature dependent current source.
Dependencies are inferred from the claim text.