Differential RF Amplifier Biasing Without External SAW Filters

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Solution Overview

Problem

Incorporating a filter circuit that suppresses signals in bands other than the desired band into a semiconductor chip is challenging due to the inability to integrate SAW or dielectric filters, leading to increased component count and mounting area in radio signal processing circuits.

Innovation Solution

A semiconductor integrated circuit with a voltage generator that supplies a stable bias voltage to a fully differential amplification circuit, allowing it to maintain normal operation even when input voltages fluctuate, eliminating the need for external filters by using a passive mixer and low-noise amplification circuit.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If SAW or dielectric filters are used to suppress signals in bands other than the desired band, then signal filtering performance is improved, but the component count and mounting area increase due to inability to integrate into semiconductor chip

Engineering Contradiction:

Improvesignal filtering performanceVSAvoidcomponent count and mounting area

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent replaces physical SAW or dielectric filters with an electronic filtering mechanism implemented through a fully differential amplification circuit. This circuit uses feedback paths with resistors and capacitors to create frequency-selective filtering action, substituting mechanical/physical filter structures with electronic circuitry that can be integrated on a semiconductor chip.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The fully differential amplification circuit performs multiple functions simultaneously: it provides signal amplification, common-mode noise rejection, and frequency-selective filtering. By combining these functions in a single integrated circuit block, the patent eliminates the need for separate external filter components while maintaining signal quality.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If external filters are used to maintain signal quality, then signal quality is improved, but the circuit size and component count increase

Engineering Contradiction:

Improvesignal qualityVSAvoidcircuit size

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent merges the filtering function with the amplification function by implementing frequency-selective feedback paths within the fully differential amplification circuit. The feedback networks containing resistors and capacitors create filtering action that is integrated into the same circuit block that performs amplification, eliminating the need for separate external filter components.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The filtering functionality is nested within the amplification circuit structure. The feedback paths with RC components are embedded inside the operational amplifier circuit, creating a compact integrated solution where the filter is contained within the amplifier block rather than being a separate external component.

Inventive Principle:

Principle #7Nested doll (Nesting)

3Stability of the object's composition

If a voltage generation circuit is added to supply stable bias voltage, then circuit stability is improved, but the circuit complexity increases

Engineering Contradiction:

Improvecircuit stabilityVSAvoidcircuit complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The fully differential amplification circuit generates its own stable bias voltage through an integrated voltage generation circuit that is part of the operational amplifier block. This self-contained voltage reference eliminates the need for external voltage regulation components while maintaining stable operation of the circuit.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The operational amplifier circuit is designed to perform multiple functions including signal amplification, filtering, and voltage reference generation. By integrating the voltage generation circuit within the same block, the patent provides stable biasing without adding separate external voltage regulation components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8816766B2Semiconductor integrated circuit, and reception apparatus and radio communication terminal including semiconductor integrated circuit

Publication Date: 2014.08.26 RENESAS ELECTRONICS CORP

AI summary

A semiconductor integrated circuit includes: a first capacitance element and a second capacitance element; a first amplification circuit that amplifies a potential difference of a first voltage signal and a second voltage signal supplied via the first capacitance element and the second capacitance element, respectively, to output a first amplification signal and a second amplification signal; a first resistance element that feeds back the first amplification signal to one input terminal of the first amplification circuit; a second resistance element that feeds back the second amplification signal to another input terminal of the first amplification circuit; a voltage generator that generates a predetermined voltage; and a third resistance element that transmits the predetermined voltage generated by the voltage generator to each input terminal of the first amplification circuit.