BIPOLAR TRANSISTORS
The unipolar transistor is an element whose internal resistance can vary depending on the input signal applied, this variation caused makes it capable of regulating the current through the circuit that is connected. It is formed by the union of three pills semiconductor (N or P) linked together, being the central than at the ends and in this way, we can find NPN or PNP transistors. The central bar is the base and is the smallest of all and the end are the emitter and collector (higher than the issuer). The transmitter heavily doped carriers, and its mission is to inject them into the base. The base is lightly doped (less doped), and here is where they spend the carriers coming from the emitter collector road, in this way creates a current. The collector is more doped than the base, but unless the issuer, and this is who collects the carriers coming from the issuer and has not collected the base.
transistor is true in any respect to voltages and currents, the following:
Polarization is to get the appropriate voltages at each point of the circuit, the desired current and the point of rest (or work) Q. All this involves connecting the transistors to some resistance that, through the voltage drop produced in them, they could institute the intended values \u200b\u200band stability. This will be done from DC voltages.
is always located in the load line and within a curve, specifying a certain collector current Ic and a specific collector-emitter voltage Vce.
*
cutting area This area always have Ib = 0, Ic = 0, Vce = Vcc. The transistor behaves almost like an open circuit.
* Hotspot
This is where the transistor usually works, being the area where the transistor amplifier, fulfilling Ib Ic = B, Vce = 0.6 V (0.2 V for the case of germanium transistors.)
* Zone of saturation
The transistor behaves approximately like a short circuit.
Stabilization The stabilization is to prevent thermal runaway and reduce the displacement of the point. To get used methods by which an increase in collector current lead, by feedback, to a variation of another magnitude to cause a compensatory decrease of the collector current, so that the resulting increase in Ic is much smaller than Ic increased without the stabilizing system.
Q:
equation of currents:
base mesh ---> Ib = 38.87 microamps. Trt of the equation ---> Ic = 4.58 milliamps. Collector mesh ---> Vce = 5.42 volts.
current equation: Ie = Ic + Ib
Stabilization emitter resistance (Re) and voltage divider bias based (self-bias)
The electrical This circuit is very effective and is developed as follows: If we assume an increase in Ic, the voltage drop across Re increases and counteracts the increase of the current Ic because there is a decrease in the base bias voltage Vbe. R1 and R2 are the resistances for varying the working point Q and consequently the work area.
Getting the point Q:
base mesh ---> Ib = 55.11 microamps. Trt of the equation ---> Ic = 5.31 milliamperes collector mesh ---> Vce = 5 volts.
Class B Amplifier: The working point is situated on the edge of the hotspot. Only amplify the positive half cycle of the input signal, so you will need two transistors to amplify both half-cycles (positive and negative). *
If we amplify the scale can also make classification:
- Amplicen voltage. -
frequency video amplifier
BASIC POWER amplifiers, also called Power, whose mission is to deliver to the load signal great power with minimum distortion and maximum efficiency. The output impedance should be small since the load is usually a speaker (4 or 8 ohms), so these amplifiers tend to be common collector because its current gain is very high and this makes the output intensity is large enough to move the cone. There are various assemblies such as common-emitter amplifier output coupling transformer-amplifier output and push-pull output amplifier with complementary symmetry
The circuit consists of two transistors with identical characteristics but different type, one PNP and one NPN (from Hence the name of "complementary"). Class B are polarized so that each transistor lead in opposing half cycles of the input signal.
As can be seen on the oscilloscope, the output signal has a distortion called crossover distortion. This distortion is a more than it can be in any electronic circuit, the most common (and all undesirable) the frequency, phase or amplitude.