question: Why do you need a Transistor to amplify your signals? Why can't you directly add an extra power source to your signal circuit to boost/amplify your signals in circuit?
comment: Say you have a signal that goes rapidly changes from 0 V to 1 V. Then you add a 10 V battery to add to that voltage - you now have a signal that goes from 10 V to 11 V instead. That isn't any more useful than the signal you started with. An amplifier doesn't add voltage, it multiplies it. So If you put in 1 V into a 10x amplifier, it puts out 10 V, and if you put in 0 V, it puts out 0 V as well.
passages: Providing sufficient base drive current is a key problem in the use of bipolar transistors as switches. The transistor provides current gain, allowing a relatively large current in the collector to be switched by a much smaller current into the base terminal. The ratio of these currents varies depending on the type of transistor, and even for a particular type, varies depending on the collector current. In the example light-switch circuit shown, the resistor is chosen to provide enough base current to ensure the transistor will be saturated.
   Loss from subthreshold leakage can be reduced by raising the threshold voltage and lowering the supply voltage. Both these changes slowdown the circuit significantly. To address this issue, some modern low-power circuits use dual supply voltages to improve speed on critical paths of the circuit and lower power-consumption on non-critical paths. Some circuits even use different transistors (with different threshold voltages) in different parts of the circuit, in an attempt to further reduce power consumption without significant performance loss.
   Solid state devices, either discrete transistors or integrated circuits, are universally used for new transmitter designs up to a few hundred watts. The lower level stages of more powerful transmitters are also all solid state. Transistors can be used at all frequencies and power levels, but since the output of individual devices is limited, higher power transmitters must use many transistors in parallel, and the cost of the devices and the necessary combining networks can be excessive. As new transistor types become available and the price drops, solid state may eventually replace all valve amplifiers.
   The main disadvantage of TTL with a simple output stage is the relatively high output resistance at output logical "1" that is completely determined by the output collector resistor. It limits the number of inputs that can be connected (the fanout). Some advantage of the simple output stage is the high voltage level (up to V) of the output logical "1" when the output is not loaded.
   While not fundamental to circuit operation, diodes connected in series with the base or emitter of the transistors are required to prevent the base-emitter junction being driven into reverse breakdown when the supply voltage is in excess of the "V" breakdown voltage, typically around 5-10 volts for general purpose silicon transistors. In the monostable configuration, only one of the transistors requires protection.
  
  Section::::Astable multivibrator.:Astable multivibrator using an op-amp.
   Intel explains: "The additional control enables as much transistor current flowing as possible when the transistor is in the 'on' state (for performance), and as close to zero as possible when it is in the 'off' state (to minimize power), and enables the transistor to switch very quickly between the two states (again, for performance)." Intel has stated that all products after Sandy Bridge will be based upon this design.
   The TTL "totem-pole" output structure often has a momentary overlap when both the upper and lower transistors are conducting, resulting in a substantial pulse of current drawn from the power supply. These pulses can couple in unexpected ways between multiple integrated circuit packages, resulting in reduced noise margin and lower performance. TTL systems usually have a decoupling capacitor for every one or two IC packages, so that a current pulse from one TTL chip does not momentarily reduce the supply voltage to another.
   Despite the need for relatively high programming and erasing voltages, virtually all flash chips today require only a single supply voltage and produce the high voltages using on-chip charge pumps.
  
  Over half the energy used by a 1.8 V NAND flash chip is lost in the charge pump itself. Since boost converters are inherently more efficient than charge pumps, researchers developing low-power SSDs have proposed returning to the dual Vcc/Vpp supply voltages used on all the early flash chips, driving the high Vpp voltage for all flash chips in a SSD with a single shared external boost converter.
   For low noise at narrow bandwidth the higher input resistance of the FET is advantageous.
   As transistors become smaller on chips, it becomes preferable to operate them on lower supply voltages, and the lowest supply voltage is often desired by the densest chip, the central processing unit. In order to supply large amounts of low-voltage power to the Pentium and subsequent microprocessors, a special power supply, the voltage regulator module began to be included on motherboards. Newer processors require up to 100 A at 2 V or less, which is impractical to deliver from off-board power supplies.
   Due to the output structure of TTL devices, the output impedance is asymmetrical between the high and low state, making them unsuitable for driving transmission lines. This drawback is usually overcome by buffering the outputs with special line-driver devices where signals need to be sent through cables. ECL, by virtue of its symmetric low-impedance output structure, does not have this drawback.
   The IGBT is a recent component, so its performance improves regularly as technology evolves. It has already completely replaced the bipolar transistor in power applications; a power module is available in which several IGBT devices are connected in parallel, making it attractive for power levels up to several megawatts, which pushes further the limit at which thyristors and GTOs become the only option. Basically, an IGBT is a bipolar transistor driven by a power MOSFET; it has the advantages of being a minority carrier device (good performance in the on-state, even for high voltage devices), with the high input impedance of a MOSFET (it can be driven on or off with a very low amount of power).
   A breakthrough in power electronics came with the invention of the MOSFET (metal-oxide-semiconductor field-effect transistor) by Mohamed Atalla and Dawon Kahng at Bell Labs in 1959. Generations of MOSFET transistors enabled power designers to achieve performance and density levels not possible with bipolar transistors. Due to improvements in MOSFET technology (initially used to produce integrated circuits), the power MOSFET became available in the 1970s.
   Section::::Simplified operation.
  
  The essential usefulness of a transistor comes from its ability to use a small signal applied between one pair of its terminals to control a much larger signal at another pair of terminals. This property is called gain. It can produce a stronger output signal, a voltage or current, which is proportional to a weaker input signal; that is, it can act as an amplifier. Alternatively, the transistor can be used to turn current on or off in a circuit as an electrically controlled switch, where the amount of current is determined by other circuit elements.
   On 15 December 1947, "When the points were, very close together got voltage amp about 2 but not power amp. This voltage amplification was independent of frequency 10 to 10,000 cycles".
   In France, during the war, Herbert Mataré had observed amplification between adjacent point contacts on a germanium base. After the war, Mataré's group announced their "Transistron" amplifier only shortly after Bell Labs announced the "transistor".
   Because signals don't have to move as far, the clock can tick much faster. ..
  
  There is still a need to convert the result to binary at the end of a calculation, which effectively just means letting the carries travel all the way through the number just as in a conventional adder. But if we have done 512 additions in the process of performing a 512-bit multiplication, the cost of that final conversion is effectively split across those 512 additions, so each addition bears 1/512 of the cost of that final "conventional" addition.
  
  Section::::Drawbacks.
   transistors, clocked at over 1 GHz, means manual power optimization would be hopelessly slow and all too likely to contain errors. Computer-aided design (CAD) tools and methodologies are mandatory.
   If an adding circuit is to compute the sum of three or more numbers, it can be advantageous to not propagate the carry result. Instead, three-input adders are used, generating two results: a sum and a carry. The sum and the carry may be fed into two inputs of the subsequent 3-number adder without having to wait for propagation of a carry signal. After all stages of addition, however, a conventional adder (such as the ripple-carry or the lookahead) must be used to combine the final sum and carry results.
  
  Section::::Binary adders.:3:2 compressors.
   Finally, there are several techniques for reducing the number of state changes associated with a given computation. For clocked- logic circuits, clock gating technique is used, to avoid changing the state of functional blocks that are not required for a given operation. As a more-extreme alternative, the asynchronous logic approach implements circuits in such a way that a specific externally supplied clock is not required. While both of these techniques are used to different extents in integrated circuit design, the limit of practical applicability for each appears to have been reached.
  
  Section::::Electronics.:Wireless communication elements.
   Hamm's paper was also countered by Dwight O. Monteith Jr and Richard R. Flowers in their article "Transistors Sound Better Than Tubes", which presented transistor mic preamplifier design that actually reacted to transient overloading similarly as the limited selection of tube preamplifiers tested by Hamm. Monteith and Flowers said: "In conclusion, the high voltage transistor preamplifier presented here supports the viewpoint of Mintz: 'In the field analysis, the characteristics of a typical system using transistors depends on the design, as is the case in tube circuits. A particular 'sound' may be incurred or avoided at the designer's pleasure no matter what active devices he uses.'"
   Detector and power rectifiers could not amplify a signal. Many efforts were made to develop a solid-state amplifier and were successful in developing a device called the point contact transistor which could amplify 20db or more. In 1922 Oleg Losev developed two-terminal, negative resistance amplifiers for radio, and he perished in the Siege of Leningrad after successful completion. In 1926 Julius Edgar Lilienfeld patented a device resembling a field-effect transistor, but it was not practical. R. Hilsch and R. W. Pohl in 1938 demonstrated a solid-state amplifier using a structure resembling the control grid of a vacuum tube; although the device displayed power gain, it had a cut-off frequency of one cycle per second, too low for any practical applications, but an effective application of the available theory. At Bell Labs, William Shockley and A. Holden started investigating solid-state amplifiers in 1938. The first p–n junction in silicon was observed by Russell Ohl about 1941, when a specimen was found to be light-sensitive, with a sharp boundary between p-type impurity at one end and n-type at the other. A slice cut from the specimen at the p–n boundary developed a voltage when exposed to light.
   Section::::Driving MOS transistors.
  
  A N-MOSFET/IGBT needs a significantly positive charge ("V  V") applied to the gate in order to turn on. Using only N-channel MOSFET/IGBT devices is a common cost reduction method due largely to die size reduction (there are other benefits as well). However, using nMOS devices in place of pMOS devices means that a voltage higher than the power rail supply (V+) is needed in order to bias the transistor into linear operation (minimal current limiting) and thus avoid significant heat loss.
   Section::::Input impedance.
  
  In analog circuit designs, a bootstrap circuit is an arrangement of components deliberately intended to alter the input impedance of a circuit. Usually it is intended to increase the impedance, by using a small amount of positive feedback, usually over two stages. This was often necessary in the early days of bipolar transistors, which inherently have quite a low input impedance. Because the feedback is positive, such circuits can suffer from poor stability and noise performance compared to ones that don't bootstrap.
   Figure 3 shows a MOSFET common-source amplifier with an active load. Figure 4 shows the corresponding small-signal circuit when a load resistor "R" is added at the output node and a Thévenin driver of applied voltage "V" and series resistance "R" is added at the input node. The limitation on bandwidth in this circuit stems from the coupling of parasitic transistor capacitance "C" between gate and drain and the series resistance of the source "R". (There are other parasitic capacitances, but they are neglected here as they have only a secondary effect on bandwidth.)
  