The inverting input is held low through a 10K resistor when the circuit is powered on but not being used. Whenever a measurement is being made (including calibration measurements where IN is floating), that resistor is disconnected. The circuit is used to measure currents in the nanoamp range. A few mV on the output is significant. Constant offsets are not
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really a problem, as they can easily be calibrated out by measuring the output with an open input and subtracting that from subsequent measurements. SW1A and SW1B are different poles of the same CMOS switch (ADG1236). They are switched together to select the feedback resistor, which determines the gain of the converter. The maximum leakage current is 1 nA on source and drain pins, on or off. The switch not shown (for holding the inverting input low through a 10K resistor) has similar performance. Typical leakage currents are very small (< 0. 1nA). The problem I am having is that in some batches of boards, some (or all) of these circuits have large offsets which decay slowly when powered on. However, most boards are perfectly stable at all times, with small offsets. When the afflicted boards are powered on, the offset will slowly (after hours of days) stabilize to ~5 mV. After power is removed, the offset accumulates again, so when powering it on after a couple days of being off, it`s high again. Each board has a bunch of these circuits on it. In the first batch of 5 boards, all of them were affected. In the next batch, none were affected. In the most recent batch, each board has one affected circuits, and it isn`t always the same one. At the worst case, the maximum leakage currents of all the analog switches would be 1. 2nA, resulting in a 12 mV offset at the highest gain setting, so I don`t think that can account for all...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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