1 / 33

Operational Amplifiers

Operational Amplifiers. Brandon Borm Shelley Nation Chloe Milion. Outline. Introduction Background Fundamentals of Op-Amps Real vs. Ideal Applications. What is an Op-Amp. Low cost integrating circuit consisting of transistors resistors capacitors

sheri
Download Presentation

Operational Amplifiers

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. Operational Amplifiers Brandon Borm Shelley Nation Chloe Milion

  2. Outline • Introduction • Background • Fundamentals of Op-Amps • Real vs. Ideal • Applications

  3. What is an Op-Amp • Low cost integrating circuit consisting of • transistors • resistors • capacitors • Op-amps amplify an input signal using an external power supply

  4. Uses for Op-Amps • Op-Amps are commonly used for both linear and nonlinear applications • Linear • Amplifiers • Summers • Integrators • Differentiators • Filters (High, Low, and Band Pass) • Non-linear • Comparators • A/D converters

  5. Vacuum Tube Op-Amps • First op amps built in 1930’s-1940’s • Technically feedback amplifiers due to only having one useable input • Used in WWII to help how to strike military targets • Buffers, summers, differentiators, inverters • Took ±300V to ± 100V to power http://en.wikipedia.org/wiki/Image:K2-w_vaccuum_tube_op-amp.jpg1

  6. Solid State Discrete Op-Amps • Solid state op amps invented in 1960’s • Possible due to invention of silicon transistors and the IC • Chip and discrete parts • Reduced power input to ±15V to ±10V • Packaging in small black boxes allowed for integration with a circuit

  7. Monolithic Integrated Circuit Op-Amp • First created in 1963 • μA702 by Fairchild Semiconductor • μA741 created in 1968 • Became widely used due to its ease of use • 8 pin, dual in-line package (DIP) • Further advancements include use of field effects transistors (FET), greater precision, faster response, and smaller packaging

  8. +Vs +Vin + Vout -Vin - -Vs Features of Op-Amps • +Vin: non-inverting input • -Vin: inverting input • +Vs: positive source • -Vs: negative source • Vout: output voltage • ON: Offset Null • NC: Not Connected ON NC +Vs -Vin +Vin Vout -Vs ON

  9. Ideal Op-Amp Infinite open loop gain (GOL): Zero common mode gain Infinite bandwidth: Range of frequencies with non-zero gain Real Op-Amp Limited open loop gain: Decreases with increase in frequency Non-zero common mode gain Limited Bandwidth: Gain becomes zero at high frequencies Characteristics of Op-Amps

  10. Ideal Op-Amp Infinite slew rate Infinite input impedance No input current Zero output impedance Infinite output current Real Op-Amp Finite slew rate Large input impedance Small input current Non-zero output impedance Limited output current Characteristics of Op-Amps

  11. Summary of Characteristics

  12. Ideal Op-Amp • Active device • Infinite open loop gain • Infinite input impedance • Zero output impedance +Vs iin = 0A + Vdiff Vout = Vdiff x Gopenloop - -Vs

  13. Negative Feedback • Vout is a linear function of the input voltage • Zin = infinity Iin=0A Vdiff=0V • Modelisation of basic mathematical operation

  14. Non Inverting Circuit +Vs (1) V- - Vout = R2 x i iin = 0A + Vout (2) V- = - R1 x i Vdiff = 0V Vin - V- = V+ = Vin (2) i = -Vin/R1 0A -Vs R1 R2 i (1) Vin – Vout = -Vin x R1/R2 V- V- - Vout Vout = (1 + R1/R2) x Vin

  15. Inverting Circuit +Vs (1) V- - Vout = R2 x i iin = 0A + Vout (2) Vin - V- = R1 x i Vdiff = 0V - -Vs V- = V+ = 0 (1) i = Vin / R1 Vin R1 R2 i Vin – V- V- - Vout Vout = - R2/R1 x Vin

  16. Follower Circuit + Vs Vin Vout - Vs

  17. Summing Op-Amp • Adds analog signals Ohm’s Law: Solving for Vout:

  18. Summing Op-Amp

  19. Difference Op-Amps • Subtracts analog signals • Output voltage is proportional to difference between input voltages:

  20. Difference Op-Amp

  21. Integrator Op-Amps • Similar layout to inverting op-amp, but replace feedback resistor with a capacitor • A constant input signal generates a certain rate of change in output voltage • Smoothes signals over time • Output voltage is proportional to the integral of the input voltage:

  22. Integrator Op-Amp

  23. Differentiating Op-Amp • Similar to inverting op-amp, but input resistor is replaced with a capacitor • Accentuates noise over time • Output signal is scaled derivative of input signal:

  24. Differentiating Op-Amp

  25. Active Filters • Different types of active filters: • Low Pass • Filters out frequencies above a cutoff frequency • High Pass • Filters out frequencies below a cutoff frequency • Band Pass • Passes a range of frequencies between two cutoff frequencies

  26. Active Low-Pass Filter • Cutoff frequency:

  27. Active High-Pass Filter • Switch positioning of capacitors and resistors from low-pass filter locations to create high-pass filter.

  28. Active Band-Pass Filter • Created by connecting output of a high-pass filter to the input of a low-pass filter or vice versa. • Also can create using only 1 op-amp with feedback and input capacitors

  29. No negative feedback • Vout is a non-linear function of the differential input voltage V+ - V- • V+ - V- = Vdiff • Vout = sign(Vdiff) x Vs • Binary logic and oscillator

  30. Comparator Vout ( volts ) +Vs iin = 0A + + Vs Vout Vdiff - V+ Vdiff 0V V- -Vs - Vs

  31. Comparator

  32. Questions?

  33. References • “Operational Amplifiers.” http://en.wikipedia.org/wiki/Op_amp • “Real vs. Ideal Op Amp.” http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/opamp.html#c4 • “741 Op Amp Tutorial.” http://www.uoguelph.ca/~antoon/gadgets/741/741.html • “Op Amp History.” Analog Devices. http://www.analog.com/library/analogDialogue/archives/39-05/Web_ChH_final.pdf

More Related