Gary, Might be correct about a light bulb. Some would say it is active, hi. However, its material is not changed, just heated up. The amp meter does not change its parameters, just reacts to a signal similar to an inductor.
A diode's atoms change and react to applied signal unlike a resistor, inductor or capacitor. In a diode it must be excited by a signal to behave as a diode. Just setting around it will not have diode properties unlike a resistor that has it resistance no matter what. This is the difference. A diode changes and activity affects the performance and conditions/state of a circuit. Like in a power supply it changes its operation from forward to reverse bias. A bipolar transistor is 2 diodes exhibiting the same changes as a diode junction. Just like to operate in a controlled range. As all know a diode can be used to detect a RF signal and also generate RF mixing producing inter mod or other signal producing elements. Maybe we've beat this to death. I guess we just leave it to what each believe. 73, ron, n9ee/r >From: Gary Schafer <[EMAIL PROTECTED]> >Date: 2007/10/24 Wed AM 11:42:18 CDT >To: [email protected] >Subject: RE: RE: RE: RE: RE: RE: RE: [Repeater-Builder] Re: duplexer isolation >and reciev > >So according to your definition of "active" that would mean that a regular >old ammeter is an active device as something changes when a signal is >applied. > >That would also make a light bulb an active device as its properties change >when a signal is applied. Its resistance changes, it gives off heat and >light. > >That would also make a resistor an active device as it gives off heat when a >signal is applied. > >A capacitor could also be called an active device by that same definition as >it accumulates charge when a signal is applied. It has changed its state. > >73 >Gary K4FMX > >> -----Original Message----- >> From: [email protected] [mailto:Repeater- >> [EMAIL PROTECTED] On Behalf Of Ron Wright >> Sent: Wednesday, October 24, 2007 7:25 AM >> To: [email protected] >> Subject: Re: RE: RE: RE: RE: RE: RE: [Repeater-Builder] Re: duplexer >> isolation and reciev >> >> Jeff, >> >> Beta is the current gain of a transistor, HFE and Hfe. No one would >> design a transistor with a beta of less than one, but they do exist for >> transistors can become defective. It is common for a new transistor to >> have a beta of 100, but after hours of use decrease to 20. A good design >> recognizes this and adapts. They can also decrease to less than 1. >> Usually one replaces them, but they are still acting as a transistor. An >> emitter follower will have power gain only if the transistor has a beta, >> HFE or Hfe, greater than 1, but is active in any case. Having gain, >> voltage, current or power, does not determine if a component is active. >> It is how the component reacts to the energy. >> >> Yes diodes and transistor have junction capacitance, resistance, but get >> their properties from entirely different means than passive devices such >> as a resistor. Junction capacitance is a function of energy supplied to >> the device. A capacitor does not change its properties based on energy >> supplied, unless one exceeds its specs. A diode does. >> >> A transistor and diode change their properties based on the energy >> supplied. This makes both active. >> >> As for the Quantum Mechnicancs this was over 40 years ago. One must know >> high level calculus understanding the wave and heat flow equations to >> follow. On one of my exams the instruction was to come up with the >> equation for current flow in a diode. Only took about 3 pages. The 2nd >> question was how much current was flowing with given parameters, holes, >> doping density, and some others. If you got the first correct it was >> easy. If one goes thru these derivations one can see a diode is a very >> active device. >> >> 73, ron, n9ee/r >> >> >> >> >From: Jeff DePolo <[EMAIL PROTECTED]> >> >Date: 2007/10/23 Tue PM 08:52:14 CDT >> >To: [email protected] >> >Subject: RE: RE: RE: RE: RE: RE: [Repeater-Builder] Re: duplexer >> isolation and reciever n >> >> > >> > >> >> Sorry, but I totally disagree about a diode not being active. >> >> If having to have gain then many devices such as a transistor >> >> emitter follower with a beta of <1 would not be an active device. >> > >> >I assume you're using the term "beta" to really mean current gain of the >> >stage. On my planet, an emitter-follower stage can't have a current gain >> of >> >< 1. Please draw me a schematic of an emitter-follower circuit that >> does. >> > >> >Or better yet, point me to a data sheet for a transistor that has a beta >> >(hFE) spec of less than one. >> > >> >An emitter-follower is a current-gain stage. Assuming the voltage >> remains >> >constant (or nearly so, minus the junction drop), but current increases, >> it >> >provides POWER GAIN, which DOES make it an active stage. >> > >> >> Maybe if you had studied the equations with Quantum Mechanics >> >> for a diode you might understand this. >> > >> >You don't need quantum mechanics to show that a diode is a passive >> device. >> >But I'll indulge you; please explain how a diode (just a plain old >> silicon >> >junction diode) qualifies as an active device using quantum mechanics. >> > >> >> A diode follows some >> >> of the same equations as a transistor. >> > >> >So? A diode also "follows some of the same equations" as a capacitor, a >> >resistor, an inductor, or even a fuse for that matter depending on how >> its >> >used in a circuit. What's your point? >> > >> > --- Jeff >> > >> > >> >> >> Ron Wright, N9EE >> 727-376-6575 >> MICRO COMPUTER CONCEPTS >> Owner 146.64 repeater Tampa Bay, FL >> No tone, all are welcome. >> >> >> >> >> >> >> >> Yahoo! Groups Links >> >> >> > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
