Operational Amplifier with Dynamic Drive Current for Higher Slew Rate

Solution Overview

Problem

Conventional operational amplifiers face challenges in increasing slew rate without increasing drive current, leading to stability issues and requiring additional external terminals for parameter setting, which complicates packaging and efficiency.

Innovation Solution

The operational amplifier is configured with differential input parts, auxiliary current generators, and drive current generators to enhance slew rate without increasing drive current, and a parameter setting circuit is integrated into the semiconductor device to arbitrarily set threshold voltages and other parameters without additional external terminals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the drive current of the operational amplifier is increased to increase the slew rate, then the slew rate is improved, but the current consumption increases dramatically

Engineering Contradiction:

Improveslew rateVSAvoidcurrent consumption

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The circuit performs preliminary action by detecting input signal changes in advance and proactively adjusting the drive current before the actual slew rate limitation occurs. The detection circuit monitors the input signal and generates a detection signal that triggers current increase only when needed, rather than maintaining high current continuously.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The drive current is made dynamic rather than static. The operational amplifier automatically adjusts its drive current based on real-time input signal conditions - increasing current when sudden changes are detected and reducing it during normal operation. This dynamic adaptation resolves the contradiction between achieving high slew rate and minimizing current consumption.

Inventive Principle:

Principle #15Dynamics

2Speed

If the drive current of the operational amplifier is increased to increase the slew rate, then the slew rate is improved, but the stability (phase margin) cannot be ensured

Engineering Contradiction:

Improveslew rateVSAvoidphase margin

Core Design Contradiction:

SpeedVSStability of the object's composition

Solution Approach 1:

The drive current is made dynamic rather than static. The operational amplifier automatically adjusts its drive current based on real-time input signal conditions - increasing current when sudden changes are detected and reducing it during normal operation. This dynamic adaptation resolves the contradiction between achieving high slew rate and minimizing current consumption.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The circuit performs preliminary action by detecting input signal changes in advance and proactively adjusting the drive current before the actual slew rate limitation occurs. The detection circuit monitors the input signal and generates a detection signal that triggers current increase only when needed, rather than maintaining high current continuously.

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If external terminals are added for parameter setting, then the threshold voltage can be set, but the package size increases and complexity increases

Engineering Contradiction:

Improveparameter setting capabilityVSAvoidnumber of external terminals

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The operational amplifier is designed with universal adaptability through internal parameter setting circuits that can be configured through existing control terminals. The same terminals used for normal operation can also set threshold voltages and other parameters, eliminating the need for dedicated external parameter setting terminals while maintaining full functionality.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The parameter setting function is merged with the existing operational amplifier structure. Instead of adding separate external terminals for parameter setting, the circuit uses internal configuration mechanisms that work through the existing terminal infrastructure, combining multiple functions into unified terminal usage.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS8754881B2Operational amplifier and liquid crystal drive device using same, as well as parameter setting circuit, semiconductor device, and power supply unit

Publication Date: 2014.06.17 ROHM CO LTD

AI summary

The operational amplifier according to the present invention has at least one differential input part for generating a voltage signal corresponding to an electric potential difference between a positive-phase input signal and a negative-phase input signal by using a differential pair configured from a pair of transistors; an output part for generating and outputting an output signal of a logic level corresponding to the voltage signal generated by the differential input part; at least one auxiliary current generator for detecting a sudden change in the positive-phase input signal or the negative-phase input signal and generating an auxiliary current; and a drive current generator for adding together a predetermined reference current and the auxiliary current and generating a drive current of the differential input part.