Complementary Current-Reuse Preamp for Stable Low-Noise Op-Amps
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional preamp stages in electronic devices like analog-to-digital converters (ADC) suffer from noise fluctuations due to variations in power supply voltage, which are amplified by subsequent stages, degrading the signal-to-noise ratio (SNR).
Innovation Solution
A preamp stage design utilizing both PMOS and NMOS differential pairs, with diode-connected devices between the load and ground, reduces the dependence of output voltage on power supply variations, achieving increased transconductance and bandwidth while minimizing current and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional preamp stage with power supply coupling is used, then the preamp stage can be implemented with simple circuitry, but power supply variations cause noise fluctuations in the output voltage
Solution Approach 1:
The patent introduces complementary current reuse circuitry as an intermediary mechanism between the power supply and the preamp stage. This intermediary circuit captures and recycles the complementary current that would otherwise be lost, thereby stabilizing the output voltage against power supply variations without requiring complete redesign of the preamp stage architecture
Solution Approach 2:
The patent changes the electrical parameters of the preamp stage by implementing complementary current reuse, which modifies the current-voltage characteristics of the circuit. This parameter change enables the preamp to maintain stable output voltage despite power supply fluctuations, resolving the contradiction between simplicity and stability
2Speed
If amplifier bandwidth is increased through multiple-stage amplification, then the overall amplifier bandwidth is boosted, but noise from subsequent stages is amplified
Solution Approach 1:
The patent converts the harmful effect of power supply noise into a beneficial outcome by using complementary current reuse. The circuit captures the noise-carrying complementary current and recycles it in a controlled manner, transforming what would be a harmful noise source into a stabilized current path that actually improves signal quality and reduces noise propagation to subsequent stages
3Speed
If transconductance is increased to boost bandwidth, then amplifier bandwidth increases, but current and power consumption increase
Solution Approach 1:
The patent implements current recovery by capturing the complementary current that would otherwise be discarded to ground. This recovered current is then reused to provide the necessary bias currents for the preamp stage, enabling high transconductance and bandwidth performance without proportionally increasing power consumption from the supply
Data Source
AI summary
An apparatus includes a preamplifier stage to receive a power supply voltage and generate an output based upon an input. In particular, the preamplifier stage includes a biasing device coupled between the output and a ground node to bias a DC voltage level of the output independently of the power supply voltage. The preamplifier stage also includes a complementary circuit to receive the input and generate the output. The complementary circuit reuses a current through the preamplifier stage to provide an increased transconductance of the preamplifier stage for a given current level.