Here's my two pennor'th: if you parallel transistors, you increase the depletion capacitance of the junctions by 2x. However, the diffusion capacitance generally dominates in forward bias. If the total load seen remains the same as it was originally, each device sees only half the current, so only has half the diffusion capacitance, meaning, the total is the same. So the driver has to drive a larger collector-base capacitance but not so much base-emitter.
There can be problems parallelling devices with parasitics, which may need base stopper resistors and capacitors to tie the bases (NPN/PNP) together.
If you plan to halve the load impedance (double the output current) then yes, the driver will see a doubled everything,and has to be able to handle it (or parallel the drivers too).
There can be problems parallelling devices with parasitics, which may need base stopper resistors and capacitors to tie the bases (NPN/PNP) together.
If you plan to halve the load impedance (double the output current) then yes, the driver will see a doubled everything,and has to be able to handle it (or parallel the drivers too).
A bipolar transistor (bjt) is a current driven current source - the output current is modulated by the input current. Everything is nonlineair: exponential, Occam's razor is a tool to converge to a stable result.
A field effect transistor (jfet/mosfet) is a voltage driven current source - the output current is modulated by the input voltage. Everything is nonlineair: at best quadratic, Occam's razor is a tool to converge to a stable result.
In the last odd fourthy plus years in electronics, I've never regarded a transistor as a attenuator of energy.
There is no transcendency in physics, as there is no such like wielding a horseshoe in fire.
Since the art of forging was discovered, it was hailed as a magic art, wizards being able to extract metal from earth, forming it in ploughs or swords. A secret craft, mythologized by the unknown mass. Still in fashion today, like electronics, quantum mechanics, any market economy, propaganda, marketing, social media, warfare... the list is endless.
A field effect transistor (jfet/mosfet) is a voltage driven current source - the output current is modulated by the input voltage. Everything is nonlineair: at best quadratic, Occam's razor is a tool to converge to a stable result.
In the last odd fourthy plus years in electronics, I've never regarded a transistor as a attenuator of energy.
There is no transcendency in physics, as there is no such like wielding a horseshoe in fire.
Since the art of forging was discovered, it was hailed as a magic art, wizards being able to extract metal from earth, forming it in ploughs or swords. A secret craft, mythologized by the unknown mass. Still in fashion today, like electronics, quantum mechanics, any market economy, propaganda, marketing, social media, warfare... the list is endless.
My view of a bipolar is that it is voltage driven. The carrier concentrations depend on the exponential of the junction voltage. Base current is a by-product of having holes injecting into the emitter (in an NPN) , which can't be avoided.
But a base current will set up a certain voltage on the B-E junction which in turn sets the collector current, which is why many think it is a "current driven device".
Power FEts are not quadratic because the gate field is high and causes mobility reduction, which tends to make it more linear than it ought to be. Although not linear, they are a little more so than a bipolar.
But a base current will set up a certain voltage on the B-E junction which in turn sets the collector current, which is why many think it is a "current driven device".
Power FEts are not quadratic because the gate field is high and causes mobility reduction, which tends to make it more linear than it ought to be. Although not linear, they are a little more so than a bipolar.
Wrong template.
Nor BJT is a current driven, nor FET is a voltage driven, nor one of them is a current source in a follower (common collector or common drain circuit) configuration.
Really both of them performs as a voltage source with more or less output resistance seen by load.
Really both of them are combined voltage+current driven with slightly different manner of operation due to parasitic capacitances and/or bias input current based on source/load impedance.
Hm, real numbers are 'subtle and transcendental'.... What are complex numbers, groups, vector spaces, calculus, series, if I may ask? Calculus is based on infinitesimal increments. You know what infinitesimal is? It is is an infinitely small quantity.N101N said:
Mathematical proof shows that the square root of a negative number does not exist, yet, in the 16th century, a genius found, basing on the hypothetical square root of -1, there is a whole field of mathematics with its own rules. You know what, your very electronics you use, have been developed by extensive use of the properties of complex numbers!
Complex numbers are not orderable, much unlike real numbers. So, it is a logical fallacy to claim, Z > 0, Z < 0 or Z = 0 (Z stands for any complex number). For any real number, one of the three statements must be true.
Lastly, the differential D(x) of exp(x) is equal to the function itself. That is, D(x) = exp(x). Let us denote, D(x) by D1(x), where D1 stands for the first derivative. The nth derivative is exp(x). Let us write this as Dn(x) = exp(x). Extending this, implies the infinite derivate of exp(x), is the function itself!
Mathematics is a tool, just like a lathe or an oscilloscope, without it life would have been different, but harder. Technology depends on it.
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So, after some 40+ years in electronics, it proves on diyAudio (of all ahum places) all used formulas and models I have used sofar are wrong, only by extreme coincidence rendering to right values, solutions and answers by accidence! If gifted by such luck, I better buy me a lottery ticket instead posting nonsense here.
Sure, with three singulars and five compounds, no one can find the sixth compound when stuck to concrete templates. Do not read the profile or signature.
Ok.
Choose the correct statement, please, from your formulas and models:
1. Base current are prime while Vbe voltage drop are parasitic.
2. Vbe voltage are prime while base current are parasitic.
In any PN junction, the presence of a Potential Barrier is indispensable. In forward bias condition, with a voltage of opposite polarity applied to the junction diode, an increment of ionic charge (current) takes place at the negative terminal of the diode.
Also under reverse bias, a Potential Barrier that opposes the applied voltage (force) will necessarily develop. In order for that to happen, strong covalent bonds need to be broken. They do not break voluntarily nor easily, must be forced to do so.
In place of the lousy semantics like "driven", "electronic and radiative excitation" would be a more suggestive nomenclature. The important acceleration of electric charge is accomplished by electromagnetic force fields.
Also under reverse bias, a Potential Barrier that opposes the applied voltage (force) will necessarily develop. In order for that to happen, strong covalent bonds need to be broken. They do not break voluntarily nor easily, must be forced to do so.
In place of the lousy semantics like "driven", "electronic and radiative excitation" would be a more suggestive nomenclature. The important acceleration of electric charge is accomplished by electromagnetic force fields.
I guess whether you call something a voltage-driven device or a current-driven doesn't really matter since the two are related. I find it helpful to think of driving power transistors in terms of charge transfer.
Switching MOSFETs are often described in terms of Id vs gate (to source) charge; a charge-driven approach. A bipolar is also charge-driven except that it continually leaks charge rather than only integrating it. Because transistors store charge they have a capacitive characterstic. And a bipolar will turn itself off via its own charge leakage so can be "push" driven as in a darlington, but a MOSFET has no such leakage so needs to be "push-pull" driven.
Switching MOSFETs are often described in terms of Id vs gate (to source) charge; a charge-driven approach. A bipolar is also charge-driven except that it continually leaks charge rather than only integrating it. Because transistors store charge they have a capacitive characterstic. And a bipolar will turn itself off via its own charge leakage so can be "push" driven as in a darlington, but a MOSFET has no such leakage so needs to be "push-pull" driven.
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