Discussion Overview
The discussion revolves around strategies to reduce output drift in a voltage amplifier, specifically when the load resistance approaches the input impedance of the amplifier. The context includes technical considerations related to instrumentation amplifiers and their performance under varying load conditions.
Discussion Character
- Technical explanation
- Debate/contested
- Experimental/applied
Main Points Raised
- One participant notes that output drift is negligible with a 100 kOhm load but becomes significant with a 100 MOhm load, prompting a request for tricks to limit this drift.
- Another participant questions the necessity of such a high load resistance, suggesting a need for clarification on the application.
- A participant clarifies that the high resistance is dictated by physical limits of the samples being characterized, which can be as high as 10 GOhm.
- Terminology confusion arises regarding source and load impedance, with one participant correcting themselves to identify the sample resistance as the source impedance.
- Suggestions are made to use a higher impedance operational amplifier and to implement "guarding" techniques to minimize leakage into the summing junction.
- Another participant emphasizes the importance of understanding the source of drift, suggesting environmental factors and the need for proper shielding and grounding practices.
- A recommendation is made to use an Electrometer Amplifier as a unity gain buffer before the AD625 instrumentation amplifier to mitigate drift, along with suggestions for proper input pin management to avoid contamination currents.
Areas of Agreement / Disagreement
Participants express differing views on the causes of output drift and the best methods to address it. There is no consensus on a single solution, and multiple strategies are proposed without agreement on their effectiveness.
Contextual Notes
Participants highlight the complexity of the issue, noting that the source of drift may involve various factors such as environmental noise, grounding practices, and the specific characteristics of the instrumentation amplifier used. Limitations in understanding the application context may affect the proposed solutions.