Operational Amplifier Feedback for Circuit Test Voltage
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Solution Overview
Problem
Current circuit test systems face challenges in efficiently providing accurate DC voltages and high-voltage waveforms to test channels due to limitations in DC supplies, complex and costly interface boards, and the unavailability of central parametric measurement units for DC voltage generation, which affects test parallelism and increases system complexity.
Innovation Solution
The method involves configuring an operational amplifier in a test system to respond to remote or local feedback depending on the stimulus required, using a switching network and programmable loads to apply DC voltages or high-voltage waveforms to test pins, with a Kelvin sense approach for accurate DC voltage delivery and high-speed waveform capability, minimizing output impedance and leveraging existing high-voltage drivers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DC supplies are provided through special test channels with switches to connect to DC supplies, then accurate DC voltages can be applied to test pins, but the number of DC supplies and special test channels is limited, resulting in complex and expensive interface boards
Solution Approach 1:
The operational amplifier is configured to serve multiple functions: it can provide accurate DC voltages when configured with remote feedback for DC supply modes, and high-voltage waveforms when configured with local feedback for waveform generation modes. This multi-functionality eliminates the need for separate special test channels and DC supplies, simplifying the interface board design while maintaining measurement precision.
2Adaptability or versatility
If multiple DC supplies are provided to meet different DUT requirements, then various DC voltage levels can be applied, but the system becomes more complex and costly with additional components like mechanical relays or analog switches
Solution Approach 1:
The system dynamically reconfigures the operational amplifier's feedback connections based on the required voltage level. The switching network dynamically connects or disconnects the feedback path to achieve different DC voltage levels or high-voltage waveforms. This dynamic reconfiguration allows a single operational amplifier to replace multiple fixed DC supplies, reducing system complexity while maintaining adaptability.
3Power
If high-voltage drivers are used to provide DC voltages, then high-voltage capability is achieved, but voltage drop across output impedance makes this approach undesirable for substantial current loads
Solution Approach 1:
The operational amplifier employs feedback mechanisms to compensate for voltage drops. When configured for DC supply modes with remote feedback, the system monitors the actual voltage at the test pin and adjusts the operational amplifier's output accordingly. This feedback approach ensures accurate DC voltage delivery even under substantial current loads, overcoming the limitation of high-voltage drivers with significant output impedance.
4Measurement precision
If central PMUs are used for DC voltage generation, then accurate DC voltages can be provided, but central PMUs become unavailable for parametric measurements
Solution Approach 1:
The system segments the DC voltage generation function from the central PMU by implementing it at the per-pin level using operational amplifiers in each test channel. This segmentation allows DC voltage generation to be distributed across multiple test channels rather than centralized, enabling central PMUs to remain available for parametric measurements while still providing accurate DC voltages through the distributed operational amplifier network.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for efficient, accurate, and cost-effective provision of DC voltages and high-voltage waveforms to multiple test pins, simplifying interface designs, enhancing test parallelism, and freeing central PMUs for parametric measurements, while reducing hardware costs and complexity.
Implementation Method 1
configuring an operational amplifier in a test system to respond to remote or local feedback depending on the stimulus required
Implementation Method 2
with a Kelvin sense approach for accurate DC voltage delivery
Data Source
AI summary
In one embodiment, when a test program for testing a circuit specifies the application of a DC voltage to a particular node of the circuit, i) an operational amplifier of a circuit test system is configured to respond to remote feedback, wherein the remote feedback is responsive to a load on a circuit test system test pin that is coupled to the particular node, and ii) the DC voltage is applied to the particular node via the operational amplifier. When the test program specifies the application of a high-voltage waveform to the particular node, i) the operational amplifier is configured to respond to local feedback, wherein the local feedback is not responsive to the load on the test pin, and ii) at least a high-voltage portion of the high-voltage waveform is applied to the particular node via the operational amplifier. Other embodiments are also disclosed.