Class Audio
Audio Power Amplifier Class AB?
i have been assigned to design an AB class audio power (for the final project of a basic course in electronics)amplifier using Opamp : 741 , power transistors BD137,138 , a 12 v. supply , load resistance 8 ohm , voltage gain of 40 dB and cut-off frequency 20 Hz. desperately needing help ! where shall i begin?!
Okay, let's make sure we are talking about the same circuit. You have a 741 op amp feeding a class AB output stage. The class AB output stage consists of a push-pull transistor stage with two diodes on the transistor inputs to bias the output transistors slightly on. Is this what you have?
If so here is how I would approach it.
1. Setup the biasing of the output transistors. Normally, a resistor or current source is used to setup a current through the two diodes on the transistor inputs (some folks use transistors for these diodes). See Reference 2 for an example. This current should be sufficient to almost turn on the two output transistors. There is also something called a "rubber diode" that can be used to bias the output. See Reference 1 for an example.
2. Do you require short-circuit protection? If so, there are transistors that must go in the emitter legs of both output transistors. These resistors are used to turn-on additional transistors that will take base drive away from the output transistors. These must be sized to ensure that if the output is shorted that current is limited.
3. Now we design the op-amp stage. We will take feedback from the output all the way back to the op-amp negative input. There will be feedback resistor and an input resistor. Their ratio must be 100, which provides 40 dB of voltage gain.
4. I have not thought about the cut-off frequency for awhile. I would place a capacitor across the feedback resistor that will cause the feedback to rolloff at 20 Hz.
This Lepai Tripath-based audio amplifier is ideal for both home and car audio applications. Its small size and clean 20 watt output makes it perfect for most any auto or home audio project or DIY application where space is limited.
|
|
SanDisk microSD and microSDHC 1 GB*, 2 GB, 4 GB, 8 GB, 16 GB and 32 GB mobile memory cards are the best and most popular way to carry your music, videos, photos, games, files and applications on your mobile phone...
|
|
4000 Watts Max Power Class D Monoblock Power Amplifier, 1-OHM Stable
|
|
The Dayton Audio DTA-100a provides 50 watts of clean Class T digital power per channel, a built-in headphone amplifier, and two stereo inputs to connect all your portable and permanent audio devices.
|
|
Starting at 4GB, microSDHC cards offer higher storage for more music, more videos, more pictures, more games, more of everything you need in today's mobile world. The microSDHC card allows you to maximize today's revolutionary mobile devices...
|
|
Get the perfect balance of speed and reliability for high definition video and faster shot-to-shot performance with SanDisk Extreme HD Video SDHC cards. Delivering Class 10 video performance with up to 30MB/sec read/write speeds, you’ll be ready to capture HD video on the latest digital point & shoot cameras and DSLRs that have high-definition video recording capabilities...
|
|
1000 Watt Monoblock Amplifier at an affordable price
|
|
Dayton Audio's DTA-1 has the heart of a serious performer in a truly portable package. A Class-T chip lets the DTA-1 produce imaging, dynamics, and sound quality that rivals tube amps. Up to 15 watts per channel is on tap to push bookshelf speakers.
|
|
"Small" is not the real story here.
Making an amplifier small is great, of course... but not if power and sound quality are sacrificed.
This is why our engineering team focused on achieving world-class fidelity first, and then on making our HD amplifiers amazingly powerful, efficient and small...
|
|
Audio Book on 4 CDs recorded by Gordon West, WB6NOA for the 2010-2014 Technician Class FCC Element 2 license examination on 4 audio CDs. Author West reviews every possible questions and answer in the FCC questin pool and provides a fun, educational answer explanation...
|
|
Every one of us, as serious student of the Bible, would like answers and multiple perspectives on how we can interpret the difficult verses of the Bible. For example, what does it mean to blaspheme the Holy Spirit, or where did Lot's wife come from, or who is the male child of Rev. 12? The list goes on and on. Although we might be involved in a Bible study group at church, or even belong to something more involved like Bible Fellowship International, often times the depth we are searching for it really not there. Enrolling into a Bible College can help us to understand better the Word of God and it's more difficult passages.
One suggestion is for us to consider enrolling in a Bible College in our home state, whether that be California, Texas, Michigan, Alabama, Ohio, Pennsylvania, Colorado, or wherever we live in the USA. Bible Colleges offer both on-campus courses, as well as on-line courses. Classes can be taken on a full-time basis, or simply one course per quarter or semester. In many cases scholarships are available, and the price is usually within our budget.
Northern California Bible College is the type of school we're talking about. It offers advanced biblical instruction to those of us who are pastors, lay-leaders, or common parishioners; we simply want to know the Bible at a level that we're currently not receiving in our adult Bible study class in Sunday School. Some of the courses available to us include: The Life of Jesus, the Book of Acts, Romans, End-Times, Genesis, the Books of Moses, the Life of David, The Christian's Mental Health, Hermeneutics, Old and New Testament Survey, and the list goes on.
Classes can be taken for full college credit if we are wanting to earn a Bachelor of Arts degree in Biblical Studies. Or, we can take classes at the Certificate Level which allows us to earn a one-year Bible diploma. This is not an official college degree, but a systematic survey of the important books of the Bible. If we only wish to attend and receive the information we can also take classes on the Audit basis.
Graduates from Northern California Bible College are scattered over the globe pastoring churches, serving as staff ministers, or becoming strong contributors at their local church. What each student from Northern California Bible College has in common is a love for the Bible and a better understanding of what it actually says.
Classes are offered on-line, or through distance learning by listening to CDs of actual recorded lectures. For those of us who learn best by sitting in a live classroom, each quarter live classes are offered in San Jose or Dublin, California. For those of us who prefer studying in the comfort of our own home, or while driving in the car, we can take the same courses through on-line or distance learning. Each live class is recorded in the classroom (DVD, CDs, Audio Cassettes, MP3) and made available to students. Student from all over the United States are currently enrolled in this user-friendly program—from Florida to New York to Arizona to Oregon, and of course California.
David Sell is a Pastor and Bible College teacher and facilitator at Northern California Bible College aE"
http://www.NCBC.net. David can also be reached at 925 846-6464.
http://ncbc.net/"> Northern California Bible College
US $250.30
