Kevin Weddle

I am looking for a frequency that is not too high. I think the oscillator circuits get too clumsy at higher frequencies. I know that the transistors exhibit strange properties at higher frequencies, but how high. There is bound to be a graph that shows this. Anything that produces variability makes it harder to get the design right. I would say somewhere in the Khertz is the most reliable. I need the designs to stay simple and predictable. The oscilloscope isn't the only device with which to measure accuracy.

I am refering to the project found on your home page. What is going on with the batteries? Please explain the relative voltages surrounding the photodetector, which is forward biased. Are the two batteries working together? Project link: http://www.electronics-lab.com/projects/pc/023/index.html

How does one go about making sense of an opamp configuration? Start with a zero bias? Would you replace the capacitors with resistors? Do you use the maximum supply voltage? What are some primary concerns when designing an opamp?

I just read that the PS2 system is bidirectional and that this is an improvement. When they talk about I/O ports they are not implying bidirectional data. Am I right?

I think you are talking about the amplification and the voltge dividing. Zero current into the opamp and that sort of stuff. I think the gain in a nondifferential situation is high but is limited by the zero current factor. The gain would have to be high because of the small change in base current producing the output voltage.

I am using one of the newest editions of WIndows. I work with XP and Millenium. By in do you mean an in to an out? The printer port can't receive data. Am I right?

Is a stepper motor a digital input device? Is it a DC motor? I have never seen one. Any information about them would be appreciated. I have heard that motors generate a feedback voltage. Does this happen when they change direction? What is the electronics representation of the motor in terms of inductance and resistance? One thing I know is that they polarize like magnets and cause spin.

What is the accuracy difference between using the opamp differentialy as opposed to not. It is my understanding that the inputs require changes in current to function best. The example opamp shows no signal applied to the input. I think the changes in current are too small, although the signal appears credible. Is this taking advantage of the opamp? Does the signal need to change the input current more?

A zener diode is being used as the regulator in many of your circuits. If you use the zener diode as a voltage reference only, then it becomes more accurate because of the small change in current. If you use it as a regulator, then it's less accurate. Also, if you use it as a regulator, put it right on the load instead of back behind the transistor.

You can see from the evidence, a lot of opamp configurations, that the designers are willing to put anything around an opamp. Every single one of those configurations acts differently on the bias. Does anybody else think that the opamp is being too lenient when it comes to external circuitry.

The reason it works that way is because the external current dictates the voltage. This is, apparently, always the case with an opamp. I think it's interesting that it appears to work, when you should actually bias it right. You know, of course, that the opamp will work differently depending on how you bias it. In other words I can make the thing appear to obey one law and not another or disobey both laws.

Both. Where is the ouput bias? You need a resistor to ground or a negative voltage. What you have is something other than what is intended for an opamp. What happens is an increase in voltage on the emitter causes an increase in voltage on the base. The base has to be able to maintain it's voltage against the signal. This is why it is grounded. It's like running differential signals when one signal dictates over the other rather than producing a sum. Plus, you need the output bias current.

This circuit is not biased properly. The load impedance of the opamp is too high. It will work in the end, but the response will not be that of what is intended for an opamp. You have to DC bias it correctly before you use a signal. The current ouput of the first stage is simply to low.

Is the data transfer in a parallel port unidirectional? Does anybody experience how the newer generation of Windows makes it hard to get to the C: prompt? I have seen limitations using the MSDOS prompt. Sometimes I don't even want Windows to start.

A train of waves is different from the problems associated with a coaxial cable. Standing waves aren't a problem. This is the reflection that is talked about. I think the standing wave can only cause a problem when the changing signal produces different standing waves, thus affecting the input and output bias. Only if you are serious would you find that the standing wave causes a problem.

What you are referring to is that the power in equals the power out. This is true. I constructed a voltage multiplier with some results. I replaced both of the bottom capacitors with larger ones. The load was connected final capacitor to ground. It turns out that you have to decouple to measure the ripple. The two larger capacitors worked fine. The ripple of one capacitor goes through to the other capacitor to the output. These are the DC sections with rippple. The two smaller capacitors pass the other signal but have trouble keeping charged. This results in a reduced peak voltage on the larger capacitors. But they stay charged and the ripple is reduced.

I have a question. I have read, I believe, that wave propagation down a transmission line results in a train of waves. Is this true? It would make sense that a bit originating from a long distance and appearing at the other end would not happen. Instead you have a train of waves on the line at the same time.

You don't even need modulation if you don't want to utilize the short time base. The question is, where do you want to save time. In modulation, what you are doing is compressing 5 minutes worth of data into 30 seconds. 30 seconds is the transmission time. In order to that, you have to already have the 5 minutes of data generated. So you have to store it digitally for modulation. This can be useful when you have only 5 minutes. If you are continueing to generate the data, then modulation won't do any good. Make it a high speed system with data that is already generated.

I am aware of some of the problems with designing a circuit. You want one thing, but you turn around and end up negating it. You have meaing to the signal in one part, then you lose meaning when you make additions. I have an idea to correct for the nonlinearity of the transistor curve using it's inverse function. But I don't know how it can be done. Anyway, doesn't an LC filter give you 40db reduction. I really think trial and error helps a lot when determining db. If you head in the right direction and not worry exactly about the db then you can just test it with the circuit built. It must be a sorry situation when it comes time to guess because of the limitations of the measuring oscilloscope.

I know that I am a little overwhelmed when it comes to the data on data sheets. They deal largely with external testing of the device. This is the way to go, but the schematic itself is left to guessing. I do find graphs useful when looking at it from an external testing perspective. I just wish they were a little specific in their application. For example, they could just deal with one application rather than bombard you from every angle. I suppose you are just left to take from the extensive graphs what you need. My advice to the manufacturers would be to narrow the parameters. Why operate a device at 1 gigaherts just because they have data on it?

What you would be saying is that if there is sufficient current, the voltage would have to be high. The amount of current is dependent solely on the capacitors. The voltages of the multiplier are what they are. When you load the multiplier, it takes more sections to get the volatge. In other words the load causes a drop in voltage somewhere. This is a my hunch. It's about the load contributing to an unideal situation.

I built a circuit similar to this and found that my relaxation oscillater did not give me good results. I used a NAND with feedback and a capacitor and resistor. The voltage I got was not stable enough to be considered a clock. This might be interesting to anybody trying to configure a clock circuit.

I would have to argue about current loss with voltage multipliers. The problem I saw is the number of diode capacitor sections needed to deliver a high current load.

It is a very interesting experiment to send analog data down a fiber optic cable. The luck you would have could rival that of a cable. The only problem with cable is that you are limited to about 1 gigahertz. I think you might try to modulate demodulate the signal using the LED and the photodiode before inserting the fiber optic.

I was refering to only digital. I was talking about sampling, but it does not require an AD. The data rate would still be 20k hertz too. This is just a way of using the high speed transmission. With modulation, though, instead of 5 minutes to transfer the data it only takes 30 seconds.