Common Applications of Circuits!?

Discussion in 'General Electronics Chat' started by vintageplayer, Mar 2, 2015.

  1. vintageplayer

    Thread Starter New Member

    Mar 2, 2015
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    I'm looking for common applications of transistors and op-amps. Everyone knows they are used in things such as switches, amplifiers, logic gates, comparators etc. and I have no doubt the list goes on.

    What I'm really wanting to know however, is how they are specifically applied in some "every-day" appliances. For example, how are transistors or op-amps utilised in things such as:
    • modern mobile phones
    • laptops
    • lcd tvs
    • cars
    • etc.
    Circuit schematics or general concepts of how they are applied would be of interest to me. Could I find an op-amp in a modern car? Could I find a current mirror in a laptop? Could I find a common emitter amplifier in an lcd tv?

    Any info would be great (not just specific to transistors or op-amps). I'm looking to better understand where these circuits I learnt about really exist.

    Thanks for the help.
     
  2. Alec_t

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    Googling 'schematic' will give you heaps of examples.
    Yes, yes and yes.
     
  3. vintageplayer

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    Mar 2, 2015
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    I'm after specific examples, and how they are commonly used. For example, how are op-amps used in cars? All cars or only older models? Which circuitry in a car are they used and why? If you know of any sites which i might find useful, feel free to share... Google is a large place.
     
  4. Alec_t

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    How about this site for a start, re car circuitry? (Found by googling 'automotive electronics').
    Visit any of the major electronics manufacturers' web-sites and search for Application Notes.
     
  5. vintageplayer

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    Mar 2, 2015
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    Thanks but I couldn't find anything on this site that explains how op-amps are typically applied in cars... A resource that summaries a range of applications would also be nicer. Sorry but it's not really what I'm after.
     
  6. MrChips

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    In order to answer the question "Where are opamps used in automotive electronics?",
    ask yourself "What is the function of an opamp?"

    An opamp is used to amplify a low amplitude signal.

    Here are places in an automobile where you would need to amplify a signal:
    • Oxygen sensor
    • Hydrocarbon sensor
    • NO and NO2 sensor
    • Engine temperature sensor
    • Water temperature sensor
    • Hall effect sensor
    • Tire pressure sensor
    • Seat pressure sensor
    • Accelerometer
    • Digital compass
    • GPS receiver
    • Ambient temperature sensor
    • Ambient light sensor
    • Door lock RF receiver
    • Ignition RF receiver
    • Radio receiver
    • Audio amplifier
     
  7. Alec_t

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    Here's one app note for you, mentioning a car rain-sensor.
     
  8. vintageplayer

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    Mar 2, 2015
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    Yes, these could potentially contain op-amps but they could also not. If they are applied in cars to amplify signals, it would be nice to know a few examples of which model cars and why op-amps in particular are chosen for the job. Also, maybe signal amplification is not the most common application for op-amps in a car. Knowing what op-amps do, and where they might be applied, doesn't really give you a proper understanding of their applications.
     
  9. Alec_t

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    At the level of detail you seem to be asking for, any info re car electronics is likely to be proprietary.

    Here's an LCD TV manual with a schematic.
     
    Last edited: Mar 2, 2015
  10. MaxHeadRoom

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    Just do a search for Automobile CANBUS system for one.
    Max.
     
  11. vintageplayer

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    Say an engineering student asked you "where are op-amps applied?". You wouldn't say "op-amps are applied in high end cars for rain sensors" as your one example would you? It gives the wrong impression. Also, knowing what they do does not give you proper insight into where they are really applied. I'm not looking for detail - just common, everyday type applications. Something your average person would find interesting and relate to, e.g. "the op-amp summer circuit is applied exclusively in mobile phones because it is the best circuit for adding numbers when using the calculator".

    CANBUS is a communication protocol that has nothing to do with op-amps or transistors!
     
  12. bwilliams60

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    These devices you have mentioned do not use an op-amp within the device itself. Most amplification takes place within the ECM or control module for the specific circuit being used. Most of these will run on a 5V reference signal and sent a low voltage, low amperage signal back to the ECM where everything is converted to a digital signal, buffered, amplified, processed and then an outcome is decided upon by the logic processor in the ECM. This process started way back in the early 80's. In around the late 1990's and early 2000's, multiplexing was brought into play and communication between modules was introduced. Again, all signals are processed etc by the ECM.
    If the OP wants information on this, he will have to find a way to access proprietary information from one of the OEM's and that is no easy challenge. I am in this trade and I get very little info on what's inside the "box" but I can tell him that something as simple as car stereo may help him on some things. These schematics can be found with random google images search. Good luck!
     
  13. Alec_t

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    No, I wouldn't. I'd search diligently and come up with some other examples before making any generalising statements. I've given you one example. I'm sure you can find plenty of others.
     
  14. MaxHeadRoom

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    You wanted the areas that you may find op amps in an automobile??:(
    What electronics do you suppose they use?
    Max.
     
  15. MrChips

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    You are asking the wrong questions.
    It is like asking "where are resistors, transistors, opamps and microcontrollers used?"

    Are you thinking that an opamp is an 8-pin chip that you can find on a circuit board?

    Well that is the wrong question. Opamps, like resistors and transistors are integrated into the fabrication of a processor. To find them you will have to look under a microscope.
     
  16. wayneh

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    They're just about everywhere, in almost anything you would call "electronic". It's easier to list where they are NOT, the things that existed well before the transistor was invented. Light bulbs, toasters, large appliances with old-style interfaces, these things don't need transistors and you won't find any. But cars, computers, home electronics, and anything electronic more modern than ~1960 is almost guaranteed to have a transistor or an IC in it.

    Here's one very specific example. A MOSFET transistor is usually in control of the charge current for a laptop. The electronics monitor various things and make a decision about how to route power from the battery and/or AC adaptor. They control the state of a MOSFET switch.
     
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  17. WBahn

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    You don't seem to be able to make up your mind. You ask for specific examples and, when given one, you aren't satisfied because you want a general answer. Then when given a general answer you aren't satisfied because you want a specific example. Which is it?

    Let's take something as simple as a camera imager.

    http://en.wikipedia.org/wiki/Active_pixel_sensor

    In many CMOS imagers each pixel has three transistors. Each pixel has a charge storage node that changed voltage in response to the current in a photodiode. One transistor is used to reset the charge storage node, another transistor is used as a source-follower to output the voltage on the charge storage node and the third pixel is used as a switch to multiplex the output onto a column line. The signal on the column line is often buffered by an opamp. The opamp usually includes a current source (or more than one) and these are typically implemented as current mirrors.
     
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  18. vintageplayer

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    Mar 2, 2015
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    No, I would like specific examples of applications that are common.
    • By "specific" I mean the example has to be beyond a statement that they just exist. "Op-amps exist in computers" isn't a good example. "The op-amp voltage follower exists as a common standard in laptops to buffer voltage signals from the keyboard, here is a link which describes this" is a good example.
    • By "applications that are common" I mean some of their most common applications! I was dissatisfied with the rain sensor example because it was simply too niche of an application (have you ever heard of a car that did this?).
    Also, surely there is resource on the net that simply has a list of examples that satisfy this criteria? Rather than having to jump from one wiki page to the next...

    Your active pixel sensor example was great. The only thing is that the wiki link didn't mention the circuit used op-amps. How do you know an op-amp is used to buffer the signal?
     
  19. WBahn

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    Because I design CMOS imagers.

    Whether an opamp is used (and where it is used) depends on a number of factors, but it is very common to use an opamp (although it may not be a very good opamp) at some point in the processing chain. We've used opamps whose open loop gain was only about ten. You can get away with this because, in an IC, you have control over the environment that the opamp is in and can therefore use highly non-ideal devices. The same for current mirrors and bias generators -- they can be quite non-ideal as long as your overall design takes that into account.
     
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  20. Alec_t

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    I don't know in which isolated part of the world you live, but here in the UK even low-end cars (e.g. Vauxhall Corsa) have rain-sensors, for wiper control.
     
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