I would like to understand an issue with the Op Amps. The inverting and non-inverting inputs of many of the Op Amp circuits like the summing circuit of the 741 Op Amp are not biased. Is there a crossover disturtion in the out put of the circuit? How can it be corrected if any? If not, how the crossoverdisturtion was eleminated ? when I design a signal amplifier using Op Amp, do I have to consider the biasing and crossover disturtion?
Most opamps have their output transistors biased into class-AB so the crossover distortion is very low.
Except the LM358 dual and LM324 quad opamps are low power so they use not enough bias current in their output transistors. They operate in class-B. When they have 100% negative feedback their crossover distortion is reduced to "only" 3%. They recommend a load resistor to one supply voltage so that one output transistor operates in class-A for no crossover distortion.
Nigel, that's always a good advice (right tool for the job) but for us digital people (I'm sw developer, and as for the hw, I understand zeros and ones pretty good, everything other then 0/1 is big problem) maybe you can give some pointers in "how to pick the correct op-amp for the job" by pointing us to the right thread or some external link ..
Nigel, that's always a good advice (right tool for the job) but for us digital people (I'm sw developer, and as for the hw, I understand zeros and ones pretty good, everything other then 0/1 is big problem) maybe you can give some pointers in "how to pick the correct op-amp for the job" by pointing us to the right thread or some external link ..
What's the allowable voltage supply range? (0-12, -18/+18, etc).
How many op-amps in the package? (1,2 or 4)
Rail-to-Rail on the Input? Output? Is it needed?
How much current can it drive? Some can only do 10ma, others can do >100ma.
Quiescent current draw - do you need it to be low power consumption?
Gain Bandwidth Product (Is it fast enough? 1-10MHz at unity gain is typical).
Is it compensated or not? (essentially means - is it stable at near unity gains?) If uncompensated, you usually have to use a gain of 5 or more.
FET or Bipolar input type - FET inputs have extremely low input bias current. Bipolars have higher input bias current. Each type has advantages and disadvantages, but you are safer just picking a FET type.
There are lots of others. These are just some real basic criteria.
ETA: You should *never* have to worry about biasing a modern op amp. Anything from the mid 80's on should be fine.
Risking the drift into off-topic, I hope the OP will not mind and that mod's will intervene if needed, thing is, whoever did the "real" electronics use op-amps as easily as resistors or capacitors, for "0|1" people like me, op-amps are "difficult" to select, I use one op-amp in 99% cases (TL072) and that is only because I can get it in local store, saw it working somewhere, tried it, it worked. Now, I do this for fun, not for bread&butter so for me it really does not matter if the part is 1$ od 10$ .. if it could be smaller or more efficient, but, I would like to look at the page stating something like: "there are xyz important properties of op-amp, they are explained like this, op-amps are mostly grouped by this set of properties, these ones are best to use here and here, those ones are best for use in this and that type of circuitry etc... typical representative of this group is xyz###, typical representative of that gropu is xxy###..."... I was googling for it but no luck
Anyhow, I do not have a big range of op-amps available in local stores so for those I can find I mostly know what is to know (they are all ooooooold and data sheet's are available everywhere) .. but if anyone know a page like the one I just described I will be joj.
great one too ... now I can turn my head from tuple's, singlton's, mediator's and other "friends" of mine and learn bit about OP's I might even understand how some of mine projects do what they do
thanks again, now I have reading material for few days