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indulis
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Posts posted by indulis
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At resonsance, the impedance approches infinity (this of course is impossible... there are always circuit paracitics).
From the WWW...
The solution to the circuit (which is a second order differential equation) is
i(t) = Ae ^+ jωt + Be ^− jωt
Considering the initial conditions, solve for A and B.
Because there is a complex exponential (thats the "j" part), the solution represents a sinusoidal alternating current. -
No... it doesn't matter, just beware of peak-charging.
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The problem here is bandwidth... it's only as good a your sound card, and how high beyond 20KHz does it go.
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The term "ground" is often not used properly. You'll hear things like... connect it between +5V and ground... this is not correct, it should be connect it between +5V and 5V return. Power supplies are not referenced to ground, they are referenced to their return. Now it maybe that the return is connected to ground, however it is still considered referenced to it's return.
This "floating ground" to which you refer, is called a "return". -
That is not a easy question to answer unless your familiar with... transfer functions, the complex frequency domain and what bode plots are, and what they tell you.
The short answer is... the output capacitance and load resistor form a pole at a frequency of
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Unfortunatly the "twisted pair" concept (and it's benefits) have been around decades prior to the internet showing it's face. I doubt the laws of physics have changed, but
previous assertions
there just might be something there.
Hey... as soon as you made the line "dedicated" you got bandwidth, but on the flip side, it still doesn't work for everyone... nowadays there are disclamers all over the place about "... not all location may, blah, blah, blah"! That just leads me right back to... copper wire hasn't changed!! -
A 7812 can't supply anywhere near the amount of current that is needed to "spin-up" the drive, or when the head is seeking.
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What do you want to switch?
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It also relates to the reverse recovery time... in the case of a switching diode, Trr is "fast".
Besides rectifier diodes, and general purpose diodes, there's the Schottky, no Trr, a lower forward voltage, but a much higher junction capacitance. -
You have to remember all wires and circuit traces have inductance ~20nH/inch. If you need to supply large amounts of current fast, the voltage will dip. Many components (active) can't tolerate dip's below certain levels, so a "local current source", in the form of a capacitor, is added.
Pull-up resistor... the perfect example is a open collector comparator. If the output transistor isn't on, it's collector is just floating in space.
Pull-down resistor... it's like the pull-up, but it connects to a lower potential, like ground or even a negative voltage. It insures that if a node isn't "forced" to a particular level it will "tend" to go towards the pull-down potential. -
It depends on the topology that you are using... if the primary is push-pull, then the drain voltages on the MOSFET's will be 2x Vin plus any spikes from cross conduction or leakage inductance. How high these spike will be is hard to say, there are many factors to consider.
The "clamp" that your talking about is usually implemented with a zener and fast diode connected back-to-back... cathode of zener connected to the drain, the zeners anode would connect to the fast diodes anode and the fast diodes cathode would be connected to the "bulk input capacitor" / battery.
The zener value would depend on the FET's voltage rating. For a 12V system, you'd have a minimum of 24V plus spikes. A 30V FET isn't enough... the clamps/snubbers would take a beating. If it was me, I'd probably use a 60V FET and a 35V zener. I'd also use some RC/RDC snubbers. they can be connected from the drain to the "bulk input cap" or the source (gnd). It is very important to keep the snubber components very close to the FET and the connections VERY short!! -
I don't think the properties of copper wire have changed since 88, but what about the method by which the information is sent? I would have to think great strides have taken place in that arena over the past 20 years, no?
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No... that waveform looks like a simple RC integrator.
At resonance it would oscillate at 1/2*pi*(L*C)^.5 -
Technically, all switch mode converters require a load (especially converters that run in the continuous conduction mode). Voltage mode converters are even worse in regards to min load levels because of the right halfplane zero in the transfer function.
Specifically for a Cuk, I don't know. That converter topology has been covered by patents for many years, I'm not aware of anyone offering it as a off the shelf technology for standard offerings. For the most part, people just stay away. I did hear that Dr Cuk left Cal Tech and I'm not sure who holds the rights to that technology now.
Just a guess, but I think with typical values L&C, the resonance frequency would be way outside the bandwidth of the converter, and in all likelihood there is enough R around to kill the Q.
I guess not.... -
Check out a Cuk converter if you believe all switch mode power supplies have noise and ripple.
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You neglected to explain about their impedance values at resonance... and what about "Q"??
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Think about the base/collector relationship in a NPN, common emitter configuration...
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Do you mean an "inverter"??? H in L out and L in H out??
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You could try using a low on resistance (.006 ohm) logic level MOSFET.
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Base current is controlled by the value of the base bias resistor. Current through the base emitter junction will cause a collector current equal to base current times beta. Both of those currents will flow through the emitter.
It makes no difference whether the device is NPN or PNP.
Yes, I agree 1000% with that!
This isn't splitting hairs... if you were taking a test, do you think the Professor would let you slide if you were to answer a question by saying... turning transistors on and off it isn't done with electrons, its done with current... ? Do you think that would be an acceptable answer for full credit? For individuals who know, it's no big deal, they understand and make the connection, but for those that are just learning it's a very big deal. -
I know exactly what you mean and what your trying to say, but for the benefit of those that are not "well versed"...
I don't think about electrons when I have a transistor circuit. I see a resistor supplying base current to turn the transistor on and something that stops the base current to turn it off.
Current is electrons and resistors don't supply current, they limit current. -
What does
mean to you?A simplistic way of looking at it is...An NPN or PNP transistor is turned on by giving it base current
Remember this from earlier in the thread...... to turn a PNP transitor on, you have to "inject" electrons into the base and to turn a NPN transistor on you have to "pull" electrons out of the base...
This is fact, which in turn means that in one case current is flowing in, and in the other it's flowing out. -
A simplistic way of looking at it is...
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It's all about the transistors function within the circuit.
Wait until you start to explore the world of FET's... JFET, MOSFET, n, p, enhancement , depletion...
convert analog to digital
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Look up (google)
ICL7106, ICL7116