A Study on High Precision Op-Amps


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A Study on High Precision Op-Amps

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  • Welcome to the training module on A Study on High Precision Op-Amps.
  • This training module gives you introduction to High precision operational amplifier including their key features, basic block diagrams and applications.
  • Microchip Technology’s MCP605x family of operational amplifiers (op amps) have low input offset voltage of about ±150 μV and rail-to-rail input and output operation. This family is unity gain stable and has a typical gain bandwidth product of 385 kHz. The device operates with a single supply voltage which can be as low as 1.8V, whiles drawing a low quiescent current of around 30 micro amps per amplifier.
  • These features make this family of op amps well suited for single-supply, high precision, battery-powered applications. The MCP605x op amps are also suited for conditioning sensor signals in battery-powered applications.
  • An op amp can simply be defined as an analog gain block with two signal inputs, two power supply connections and one output The ideal op amp description can be separated into four basic categories: input, power supply, output, and signal transfer. The input stage of the op amp has two terminals, the non-inverting input or VIN positive and inverting input or VIN negative. For an ideal voltage feedback amplifier, both inputs need to be matched thus resulting in no leakage current, infinite input impedance, infinite common mode rejection, zero noise and zero offset voltage (VOS) between the terminals.
  • This diagram shows the op amp’s internal block diagram. As you can see, there are 3 distinct stages. The first stage or the differential input stage of the amplifier must have very high input impedance. This causes the op-amp to draw very negligible amounts of input current. The second stage or gain stage is mainly responsible for magnifying or boosting up the input signal and sending it to the output stage. The third is the output stage which delivers current to the op-amp’s load. It may or may not have short circuit protection.
  • This slide shows both an inverting and non-inverting amplifier circuit. In the inverting amplifier configuration, our signal or Vin flows through the negative input and therefore has the opposite sign to the output. The negative feedback is provided by the resistor R2 which connects the output to the input. In the non-inverting amplifier configuration, the analog input is fed through the positive input terminal. The equation for the gain is shown as Vout divided by Vin.
  • A gyrator is a four terminal or a two port device, that is designed to transform a load impedance into an input impedance and where the input impedance is proportional to the inverse of the load impedance. The gyrator network can be used to transform a load capacitance into an inductance. The primary use of a gyrator is to simulate an inductive element in a small electronic circuit or integrated circuit. The primary application for a gyrator is to reduce the size and cost of a system by removing the need for bulky, heavy and expensive inductors. Gyrators typically have higher accuracies than real inductors. This is because of the low cost of precision capacitors over inductors.
  • This page shows an instrumentation amplifier circuit, using two MCP6052. It works well for applications requiring rejection of common mode noise at higher gains. An instrumentation amplifier is a type of differential amplifier that has been outfitted with input buffers, which eliminate the need for input impedance matching and thus make the amplifier particularly suitable for use in measurement and test equipment.
  • The most frequent application for comparators is the comparison between a voltage and a stable reference. Because comparators have only two output states, their outputs are near zero or near the supply voltage. Bipolar rail-to-rail comparators have a common-emitter output that produces a small voltage drop between the output and each rail.
  • This is the MCP6XXX amplifier evaluation board. The board is designed to support inverting & non-inverting amplifiers, voltage followers, inverting & non-inverting comparators as well as inverting & non-inverting differentiators.
  • Thank you for taking the time to view this presentation on “ A Study on High Precision Op-Amps” . If you would like to learn more or go on to purchase some of these devices, you may either click on the part list link, or simply call our sales hotline. For more technical information you may either visit the Microchip Technology site, or if you would prefer to speak to someone live, please call our hotline number, or even use our ‘live chat’ online facility.
  • A Study on High Precision Op-Amps

    1. 1. A Study on High Precision Op-Amps <ul><li>Source: Microchip Technology </li></ul>
    2. 2. Introduction <ul><li>Purpose </li></ul><ul><ul><li>A Study on High Precision Op-Amps </li></ul></ul><ul><li>Outline </li></ul><ul><ul><li>Features and Application </li></ul></ul><ul><ul><li>Op-Amp Basic Block Diagram </li></ul></ul><ul><ul><li>Application Circuit (Gyrator, Instrumentation amplifier, Precision amplifier) </li></ul></ul><ul><li>Content </li></ul><ul><ul><li>11 pages </li></ul></ul>
    3. 3. Features <ul><li>• Low Offset Voltage: ±150 μV (maximum) </li></ul><ul><li>• Low Quiescent Current: 30 μA (typical) </li></ul><ul><li>• Rail-to-Rail Input and Output </li></ul><ul><li>• Wide Supply Voltage Range: 1.8V to 6.0V </li></ul><ul><li>• Gain Bandwidth Product: 385 kHz (typical) </li></ul><ul><li>• Unity Gain Stable </li></ul><ul><li>• Extended Temperature Range: -40°C to +125°C </li></ul><ul><li>• No Phase Reversal </li></ul>
    4. 4. Applications <ul><li>• Automotive </li></ul><ul><li>• Portable Instrumentation </li></ul><ul><li>• Sensor Conditioning </li></ul><ul><li>• Battery Powered Systems </li></ul><ul><li>• Medical Instrumentation </li></ul><ul><li>• Test Equipment </li></ul><ul><li>• Analog Filters </li></ul>
    5. 5. Defining The Op Amp <ul><li>The input stage of the op amp has two terminals, the non-inverting (VIN+) and inverting (VIN-) inputs. </li></ul><ul><li>The speed (SR) at which the output swings from rail to rail is instantaneous and the output impedance (ZOL or ZCL) is zero. </li></ul>
    6. 6. Op-Amp Block Diagram <ul><li>The first stage (of the op amp) is a differential amplifier. </li></ul><ul><li>The second stage is the gain stage </li></ul><ul><li>The third stage is the output stage of the operational amplifier </li></ul>
    7. 7. Inverting/ Non-Inverting Amplifier Inverting Amplifier Non-Inverting Amplifier
    8. 8. Application Circuits: Gyrator GYRATOR <ul><li>A gyrator is a four terminal or a two port device, that is designed to transform a load impedance into an input impedance. </li></ul><ul><li>The gyrator is an electric circuit which can make a capacitive circuit behave inductively. </li></ul><ul><li>The primary application for a gyrator is to reduce the size and cost of a system by removing the need for bulky, heavy and expensive inductors. </li></ul><ul><li>Gyrators will typically have higher accuracy than real inductors, due to the lower cost of precision capacitors than inductors. </li></ul>
    9. 9. Instrumentation Amplifier Two Op Amp Instrumentation Amplifier <ul><li>Instrumentation amplifiers are actually made up of 2 parts: a buffered amplifier and a basic differential amplifier. </li></ul><ul><li>The reference voltage (VREF) is supplied by a low impedance source. VREF is typically VDD/2. </li></ul><ul><li>The ideal common-mode gain of an instrumentation amplifier is zero. </li></ul><ul><li>An instrumentation amp can also be built with 2 op-amps to save on cost and increase CMRR, but the gain must be higher than 2 (+6 dB). </li></ul>
    10. 10. Precision Comparator Precision, Non-inverting Comparator <ul><li>An operational amplifier has a well balanced difference input and a very high gain. </li></ul><ul><li>A standard op-amp operating in open loop configuration (without negative feedback) can be used as a comparator. </li></ul><ul><li>When the non-inverting input (V+) is at a higher voltage than the inverting input (V-), the high gain of the op-amp causes it to output the most positive voltage it can. </li></ul><ul><li>When the non-inverting input (V+) drops below the inverting input (V-), the op-amp outputs the most negative voltage it can </li></ul>
    11. 11. MCP6XXX Amplifier Evaluation Board <ul><li>All amplifier resistors and capacitors are socket. </li></ul><ul><li>All of the component labels on board keep consistent with those on schematic generated in the Mindi™ Amplifier Designer </li></ul><ul><li>Supports all Microchip single op amps: – 8-pin PDIP package – 8-pin SOIC package </li></ul><ul><li>Test points for connecting lab equipment </li></ul><ul><li>Single supply configuration </li></ul>
    12. 12. Additional Resource <ul><li>For ordering MCP605x amplifiers, please click the part list or </li></ul><ul><li>Call our sales hotline </li></ul><ul><li>For more product information go to </li></ul><ul><ul><li>http:// www.microchip.com/wwwproducts/Devices.aspx?dDocName =en541670 </li></ul></ul><ul><li>For additional inquires contact our technical service hotline or even use our “Live Technical Chat” online facility </li></ul>