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Review of Jim Williams: AN45 Measurement and Control Circuit Collection

Download AN45 Measurement and Control Circuit Collection (1991, Linear Technology, 24 pages, 2.68 MB pdf file)

The first thing you will notice when you scroll through this app note are the baby bottles next to each circuit. Williams was writing this app note shortly after his son (p. 24) was born and he was feeding him while he designed each ciruit. So the baby bottles indicate how long it took him to design them and how complex they are.

One particular interesting circuit is the Transistor Delta VBE Based Thermometer (p. 7). The nice thing about it is that it does not require calibration, making it very attractive for low cost applications. Over a temperature range of 0-100 C it provides 0V-10V output with an accuracy of 1 C. But even if you are not interested in low cost temperature measurements you should have a look at the circuits description, it is based on a very clever design idea.

A circuit that suprised me at first was the 1.5V Powered Radiation Detector (p. 10). The trick is that a switching regulator, a transformer and finally a voltage tripler are used to raise the voltage to the 500V that are suitable for the detector. You should only build this circuit if you have experience with the safety precautions that are necessary when dealing with high voltages.

Another nice circuit is the 90uA Precision Voltage-to-Frequency Converter (p.14). For 0V-5V an output of 0kHz - 10kHz is produced with a linearity of 0.05%. If you require better linearity, Williams earlier described a circuit with 0.02% in AN23 Micropower Circuits for Signal Conditioning, p.10. But the price you have to pay is an increased current consumption of 145uA max.

You may also be interested in some other Application Notes by Jim Williams.

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