Switch-Capacitor Amplifier Bandwidth Measurement for On-Chip Testing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for measuring amplifier bandwidth are inefficient, especially in high-speed applications, as they often require expensive equipment and are not suitable for high-frequency applications due to large capacitive loading and low throughput.
Innovation Solution
A bandwidth measurement circuit using a switch-capacitor circuit with a pulse generator, pulse width monitor, and bias current control circuit, which transitions between sampling and amplification modes to determine the bandwidth of operational amplifiers by varying the pulse width of a signal holdpulse and measuring the corresponding output voltage, allowing for on-chip testing and calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional bandwidth measurement methods are used, then measurement can be performed with existing equipment, but the measurement is inefficient and requires expensive equipment for high-speed applications
Solution Approach 1:
The measurement circuit uses the amplifier under test itself to perform the measurement function. The amplifier's own output is fed back through a switch-capacitor circuit to measure its bandwidth, eliminating the need for external expensive measurement equipment and enabling self-characterization of the amplifier device.
Solution Approach 2:
The measurement circuit is designed to be universally applicable to different amplifier types and configurations. The same circuit topology can measure bandwidth of various amplifiers by adjusting the switch-capacitor circuit parameters, making the measurement system versatile rather than requiring specialized equipment for each amplifier type.
2Measurement precision
If traditional measurement equipment is used for high-frequency applications, then measurement can be performed, but large capacitive loading and low throughput occur
Solution Approach 1:
The measurement uses periodic square wave inputs and measures the amplifier response at different frequencies. By applying periodic signals and measuring the output waveform characteristics (rise time, fall time), the bandwidth can be determined through frequency-domain analysis of the time-domain response, enabling accurate high-frequency measurement without specialized RF equipment.
Solution Approach 2:
The circuit replaces traditional electrical measurement systems with a time-domain measurement approach. Instead of using complex impedance measurement equipment for high-frequency AC analysis, the system uses time-domain square wave response measurement and derives bandwidth information from the temporal characteristics of the amplifier output, substituting a simpler measurement paradigm for complex high-frequency electrical measurement.
Data Source
AI summary
A circuit for measuring a bandwidth of an amplifier includes first and second capacitors, first through third switches, and a pulse generator. First terminals of the capacitors are coupled to an amplifier input, and a second terminal of the second capacitor is coupled to an amplifier output. The first switch has a control terminal and terminals coupled to a first input node and a second terminal of the first capacitor. The second switch has a control terminal and terminals coupled to the amplifier input and output. The third switch has a control terminal, a first terminal, and a second terminal coupled to the second terminal of the first capacitor. The pulse generator has a first output coupled to the control terminal of the third switch, and is configured to vary a pulse width of a pulse signal supplied from the first output to the control terminal of the third switch.