Is there any simple method to generate a sine wave of frequency 1MHZ by using LM324 op-amp/by using filters /by using oscillators (please mention the specifications and schematic diagrams). please reply me with in 24 hours(urgent).
Is there any simple method to generate a sine wave of frequency 1MHZ by using LM324 op-amp/by using filters /by using oscillators (please mention the specifications and schematic diagrams). please reply me with in 24 hours(urgent).
The answer is no, whch isn't going to help get your homework done.
If you look at the data sheet for the LM324
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and check out page 7, you will see that amplfier runs out of small signal gain at about 1MHz (top of page, left hand side) while the large signal output swing falls below 1V at 100kHz.
If your instructor was silly enough to specify an LM324 as the op amp to use for this job you've got an easy answer to the question. Otherwise you are going to have to start out by finding a faster amplifier.
How much distortion in the sine wave can you accept? What sort of amplitude do you need? Does the frequency have to be exactly 1MHz? If so, tell us what sort of range frequencies would count as "exact" -
+/-10Hz?
How stable do amplittude and frequency have to be?
In the meantime, googling on Wien bridge and phase-shift oscillators might give you some ideas.
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The circuit given above for the Wien bridge will produce a rather distorted sine wave - there are better versions of the Wien bridge, See Jim Williams Linear Technology application note AN43 on bridge circuits
- the first half of the application notes talks about Wheatstone bridges, but the second half gets onto Wien bridges.
L is the centre-tapped primary of a transformer and can be wound on about a 10mm ferrite toroid. Rload can be coupled directly as shown, or via a secondary winding.
L+C form a tuned circuit, resonant at 1MHz.
R should be about 10k.
The load on L+C is Rload and 2R in parallel (more or less).
Make the impedance of the C about 1/10 of the effective collector-collector load then calculate the value of L for resonance.
Assume a voltage across Rtail of about 1/3 to 1/2 of Vs. Start off with a tail current of around 1-2mA dc.
A bit quick and dirty, but it oscillates quite readily and is simple to breadboard.
To the OP: It'll oscillate but I won't say you why. One thing I can tell you though: don't show this to your professor (unless he has a good sense of humor). What happens if you exchange L and C. Why?
I don't know that that's true. Given that you can make a Colpitts oscillator out of an emitter follower plus an impedance transforming network, it might be sort of fun to do the same with a 324. I bet you could make a 1 MHz oscillator out of one by using a pi network between the output and input. Not a very _good_ sine wave oscillator, but all you need is power gain, not voltage gain.
The big problem with the 324 is its slew rate, (about 0.5V/us). At 1MHz, this would limit the output amplitude to about 160mV p-p for a sinusoidal waveform.
They aren't shown, and no supply voltages are mentioned, but 6 V DC is applied to both op-amp + inputs. So I wondered if the power goes through parasitic diodes or something.
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2006 is YMMVI- Your mileage may vary immensely.
One might as well go to a single transistor, which of course works fine for the purpose.
This is once again an example of someone stuck in low frequency mentality trying to extend it to radio frequencies. Time after time, we see people needing an oscillator at 1MHz or so, and want to know why their op-amp or function generator IC doesn't work very well up there. Of course, it's because they are hitting the top of the frequency range for the device, and while the range may include 1MHz, that doesn't mean the IC designer every intended good operation up there.
Yet, they are trained in op-amp and IC solutions, so they can't see that long before op-amps came along, such an oscillator would be made with a single active element, tubes in the past, a transistor in recent decades. The 324 is a stretch at 1MHz, but it's close to DC for building an LC oscillator with a single active element. It's all perspective.
It isn't a mistake - if the OP asked the question, he isn't in state to make any sense of your kind of answer. And he still won''t get more than the 160mV out=3Dput swing set by the 0.5V/usec slew rate as worked out by TuT - I haven't checked that calculation, but it looks to ba about right.
My guess is that it would still oscillate at the same frequency, because you'd still have a 180 degree phase shift bewteeen the voltage drop across L and C, not to mention the 180 degrees across the two op amps.
I haven't tried this but here's an idea to get around that.
Use only one output of the LM324 and make a Colpitts common collector oscillator by placing an impedance in the ground line of the package. IIRC the compenation of the LM324 controls the slew rate of the output vs the ground pin.
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