Peak Detector Current Sensing for Fast Response With Low Ripple
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Solution Overview
Problem
Conventional peak detectors face a trade-off between increasing speed and minimizing ripple on their output signal, as larger transistors and higher bias currents enhance response but introduce undesirable ripple.
Innovation Solution
A peak detector that senses the charging current of a storage device and adjusts the discharge current accordingly, reducing it during charging phases and increasing it during discharge phases, using a combination of NMOS and PMOS transistors with a current source to control the active discharge device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the size of transistors 101 and 102 is increased to achieve fast charging, then the charging speed increases, but the ripple on the output signal increases
Solution Approach 1:
The patent applies dynamics by making the discharge current variable rather than constant. The discharge current is dynamically adjusted based on the charging phase: it is reduced during charging phases to minimize ripple, and increased during discharge phases to maintain fast response. This is achieved through transistors 206 and 210 that modulate the discharge current in response to the RF signal phase, resolving the contradiction between fast charging and low ripple.
2Speed
If the bias current IB is increased to achieve fast discharging, then the discharging speed increases, but the ripple on the output signal increases
Solution Approach 1:
The patent makes the discharge current dynamic by using transistors 206 and 210 to modulate the bias current IB. During charging phases, the discharge current is reduced to minimize ripple. During discharge phases, the discharge current is increased to maintain fast response. This dynamic adjustment resolves the contradiction between fast discharging and low ripple.
3Productivity
If larger transistors and higher bias currents are used to increase bandwidth, then the response time decreases, but the ripple on the output signal increases
Solution Approach 1:
The patent achieves high bandwidth with minimal ripple by dynamically adjusting the discharge current. The discharge current is reduced during charging phases to minimize ripple and increased during discharge phases to maintain fast response. This is controlled by transistors 206 and 210 that respond to the RF signal phase, allowing high bandwidth operation without the ripple penalty of continuously high bias currents.
Solution Approach 2:
The patent employs feedback mechanisms where transistors 206 and 210 sense the charging phase and adjust the discharge current accordingly. The discharge current is reduced when charging is detected and increased when discharge is needed, creating a feedback-controlled system that maintains high bandwidth while minimizing ripple.
Data Source
AI summary
A peak detector can advantageously increase its bandwidth, i.e. its charging and discharging speed, while minimizing the ripple of its output signal by sensing the charging current of a storage device. In response to that charging current, the peak detector can control a discharge current, thereby accelerating its response. For example, the peak detector can reduce a discharge current in response to an increased charging current (which indicates a charging phase) and increase the discharge current in response to a decreased charging current (which indicates a discharge phase).