A Thermocouple is a terrific way to measure temperature. The effects of temperature change on dissimilar metals produces a measurable voltage. But to make that measurement you need an amplifier circuit designed for the thermocouple being used. Linear Technology LTC 1049 Low Power Zero-Drift Operational Amplifier with Internal Capacitors While researching “Zero Drift Amplifiers” asContinue reading »
One of the acronyms you may hear thrown around is DDS which stands for Direct Digital Synthesis. DDS can be as simple as taking a digital value — a collection of ones and zeroes — and processing it through a Digital to Analog Converter (DAC) circuit. For example, if the digital source is the outputContinue reading »
When I was young the first “computer” I ever owned was an analog computer built from a kit. It had a sloped plastic case which had three knobs with large numerical scales around them and a small center-null meter. To operate it I would dial in two numbers as indicated by the scales and thenContinue reading »
A great tech not on OP Amps driving capacitance. http://www.analog.com/library/analogDialogue/archives/31-2/appleng.html
Q. How does capacitive loading affect op amp performance?
A. To put it simply, it can turn your amplifier into an oscillator. Here’s how:
Op amps have an inherent output resistance, Ro, which, in conjunction with a capacitive load, forms an additional pole in the amplifier’s transfer function. As the Bode plot shows, at each pole the amplitude slope becomes more negative by 20 dB/ decade. Notice how each pole adds as much as -90° of phase shift. We can view instability from either of two perspectives. Looking at amplitude response on the log plot,circuit instability occurs when the sum of open-loop gain and feedback attenuation is greater than unity. Similarly, looking at phase response, an op amp will tend to oscillate at a frequency where loop phase shift exceeds -180°, if this frequency is below the closed-loop bandwidth. The closed-loop bandwidth of a voltage-feedback op amp circuit is equal to the op amp’s bandwidth product (GBP, or unity-gain frequency), divided by the circuit’s closed loop gain (ACL).Continue reading »
We used to build amplifiers for digital scales (weighing Instrumentation) where we would sample a full scale voltage reference and a ground reference and from there digitally cancel out gain and baseline drift. Nowadays the amplifier itself can do a lot of this correction. We used to call these amplifiers “coppers” referring to the processContinue reading »