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 > > >
