1 / 9

EMK 310

EMK 310. Signal pre-processing. Content. Non-ideal opamps Open-loop gain Offset voltage Input resistance Frequency gain rolloff Temperature effects In resistors Voltage references Grounding PCB layout. Open-loop gain. Closed loop voltage gain equation

sybill-mclaughlin
Télécharger la présentation

EMK 310

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. EMK 310 Signal pre-processing

  2. Content • Non-ideal opamps • Open-loop gain • Offset voltage • Input resistance • Frequency gain rolloff • Temperature effects • In resistors • Voltage references • Grounding • PCB layout

  3. Open-loop gain • Closed loop voltage gain equation • Thus with Av=100 000, the ideal value of V0 if R1=10k, R2=50k and V1=1.2V is 7.2V. With the non-ideal equations V0=7.199568V • In a system operating from 0 – 7.2V, what is the maximum bit resolution where the system is still accurate?

  4. Input offset voltage • Input offset included gain equation • Thus if Vx is in a similar range as V1 the results will have a noticeable offset and introduce errors in measurements.

  5. Frequency effects • Transfer characteristic of an opamp • The higher the frequency the lower the gain, thus frequency dependant gain (=bad) need lookup table or some form of compensation.

  6. Temperature effects • Resistor temperature coefficient equation • Can calculate the resistance at specific temperatures by solving for R1 or R2. • Voltage references, voltage references can have a high TC and cause the reference voltage to drift. Can be compensated for by measuring the temperature and adjusting the value in software.

  7. Noise and grounding • Think ground wires can cause voltage fluctuations with respect to the ground potential of different devices, thus causing misreadings. • Minimize the effect of this by separating the digital and analogue ground lines.

  8. PCB layout • Separate grounds • Sandwich analogue and digital lines between a ground line • Run tracks at 90 or 45 degrees • In power supplies add filter capacitors to reduce supply noise • Try isolating sensitive circuitry!

  9. THE END! Thank you!

More Related