The new Thermocouple Amplifier feature two Analog Outputs: 10mv/C° and 4-20ma current loop output, in a NEMA rated housing. This is a Thermocouple Amplifier System Based on Linear Technology’s LT1025 – Micropower Thermocouple Cold Junction Compensator combined with the LTC1049 – Low Power Zero-Drift Operational Amplifier with Internal Capacitors this small circuit provides a basicContinue reading »
In the last video I demonstrated a Universal Active Filter that I could adjust with a dual-gang potentiometer, here I replace the potentiometer with a processor controlled solid-state potentiometer. For those that are too young to remember, we used to say “solid-state” to differentiate between that and something that used vacuum tubes… mostly we meantContinue reading »
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 »
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 »