Objective: We will be discussing Op Amp solutions to some common video applications. Along the line, we will be going over some technical details necessary to understand the requirements of amplifiers specified and used in analog video circuits. We will explore what is involved in displaying that video signal on a display screen. Next, we shall show examples of DC coupled, AC coupled, and single supply amplifier designs. The output characteristics of the op amp are discussed as they pertain to driving video specific loads. The National video MUX's will be presented along with some examples.
Length: 120 minutes
Published Date: Aug 03, 05
Step(s) to complete
- View online seminar
- Complete the suggested assignments
- Complete the online test to receive a certificate from Bob Pease
Online Seminar:
National`s Solutions for Video Applications: Part One
High Speed Amplifiers for Video Applications
About the Presentor:
Hooman Hashemi is a graduate of Santa Clara University, holding a Masters of Science in Electrical Engineering in 1988 . He obtained his B.S.E.E. from San Jose State University in 1983. Hooman joined National Semiconductor's Amplifier's Applications group in 1995. Since then he has worked on the definition and release of several general purpose and high speed devices.
About the Instructor:
Hooman Hashemi is a graduate of Santa Clara University, holding a Masters of Science in Electrical Engineering in 1988 . He obtained his B.S.E.E. from San Jose State University in 1983. Hooman joined National Semiconductor's Amplifier's Applications group in 1995. Since then he has worked on the definition and release of several general purpose and high speed devices.
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| Suggested Assignments |
Reading Assignments:
Read the following application notes to become familiar with basic power electronics design:
Research Assignments:
To learn how to effectively use National's Amplifiers WEBENCH® (Amplifiers Made SimpleSM) online design environment to design switching regulators, see the following training material broken into four parts for convenience:
Using the steps described above, design an AC coupled Non-inverting amp capable of video speeds for the following criteria:
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Input voltage = 1V
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Minimum signal freq. = 0.010 kHz
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Maximum signal frequency = 10000 kHz
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Desired gain = 2 V/V
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Reference voltage = 3.3V
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Supply voltage = +/- 3.3V
Questions:
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Read off the 3dB Bandwidth (note: You can click and drag your mouse to the right to zoom in on the viewed graphs. Click and drag to the left to zoom out).
Answer: ~80MHz
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Read off the amount of peaking in the frequency response.
Answer: ~6dB
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To what do you attribute the higher Bandwidth and lower peaking?
Answer: The lower values of resistors working against op amp input capacitance will have less impact in the range of frequencies in question.
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What is the lowest frequency that can pass through without attenuation?
Answer: With "Cc" = 180uF and Rb1= 30K, Rb2=10K, "f_minimum" is given by: f_minimum= 1 / 2*pi* (180uF) * (10K ||30K)= 0.118Hz
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Rerun simulations with "Cc" set to this value and observe the "closed loop frequency". Is this what you expected to see?
Answer: Yes, the closed loop frequency response shows that at 10Hz, the gain curve is at 3dB. That is 3dB down from the nominal 6dB in pass band. Therefore, this is what was expected with a lower value of "Cc."
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