Basic Electronics: diagram

Showing posts with label diagram. Show all posts

Showing posts with label diagram. Show all posts

Crystal Oscillators

Oscillators with Crystals Having Two Sets of Electrodes

The original crystal oscillator devised by Dr. Nicolson, as well as a number of the earlier crystal oscillators tested by Dr. Cady, employed crystals with, effectively, two pairs of electrodes. The basic circuit is shown in figure 1-156. The re quired phase inversion of, the amplifier output voltage is provided by the crystal unit operating at a mode for which the polarities of the plate and grid terminals with respect to ground are 180 degrees out of phase. The circuit shown operates the crystal unit very

Static Capacitor Exciter Stand-Alone IG for Pumping Systems

Bearing in mind the energy storage capacity or water pumping in a reservoir for later use appears to be the most appropriate ways to employ wind energy, which has a supply that depends on time, by day & season. As variable speed is useful, to tap most of the wind energy from cut-in to cut-off wind speeds, the frequency of the voltage produced by the IG varies noticeably, however the ratio V/f does not vary as that much. For induction-motor-driven pumps, such a situation is satisfactory.

Passive networks and reciprocity theorem

The ABCD parameters for a 2-port network are:

V1 = AV2 −BI2 (28)

I1 = CV2 −DI2 (29)

Figure shown below shows a two-port network whose terminals RS are short-circuited with an input voltage V across terminals PQ. Then V2 in the above equations is 0 and the equations become:

V =−BI2 (31)

and I1 =−DI2 (32)

LOW SCALE INTEGRATION

Low scale integration is a simple way from making a single transistor to putting several transistors on the same chip and linking them into straightforward circuit modules. The fact that the transistors are all on the same chip implies that their characteristics (e.g. gain) are the same. This removes the requirement of match transistors while building a circuit from various individual devices.

The very simple CMOS logic ICs are representative examples of LSI. The figure shown below is the circuit of an inverter.

SWITCHED CAPACITOR FILTERS

The principle circuit of a switched capacitor filter has been demonstrated in the figure 25.5 shown below The basic low-pass filter is made up of 2 capacitors, along with CMOS switches that are turned on alternately by a built-in clock oscillator. The clock runs at more than a few tens of kilohertz.

The switch C1 samples the input voltage when the 1st switch is closed & the 2nd switch is open. This voltage may be +ve or -ve depending on the phase of the input signal at that instant. An instant later the switches change state & the charge on C1 is equalized with the charge on C2, which came from the preceding sampling.

Differential Amplifier

The differential amplifier (shown in fig below) is also referred to as along-tailed pair. A differential amplifier contains 2 inputs namely, vIN1 and vIN2. This amplifier is used as amplifier in order to amplify the voltage difference between its inputs. When it does this, we say that it is operating in the differential mode.

BYPASS CAPACITOR

The application of an emitter resistor (R4) provides improved stability but it also gives reduced gain. When needed, we can restore the gain by wiring a high-value capacitor across R4.This keeps the emitter voltage substantially constant. Without the use of capacitor, the voltage at the emitter rises and falls with the signal. And hence it will provide negative feedback.

Lets take an example, as iB rises (tending to increase vBE),iC rises, and the emitter voltage goes up. This tends to decrease vBE, which decreases iC and resists the rise in emitter voltage. Different way of analyzing this is to say that the capacitor shunts the signal at the emitter through to the ground. This is the foremost reason why C3 is called a bypass capacitor. With this capacitor inplace, the voltage gain of the amplifier is about 280.The lower cut-off point is raised to 130 Hz, so bandwidth is somewhat reduced.

Waveform harmonics

Consider that an instantaneous voltage v be represented by the formula

v = Vm sin 2πft volts.

This is a waveform which varies sinusoidally with time t, has a frequency f, and a maximum value represented by Vm. It is normally assumed that alternating voltages have wave shapes which are sinusoidal where only 1 frequency is present. If the waveform is not happened to be sinusoidal it is called a complex wave, & whatever its shape is, itmay be split up mathematically into components called the fundamental and a number of harmonics.This process is referred to as harmonic analysis.The fundamental, which is the first harmonic, is sinusoidal and has the supply frequency, f ; the other harmonics are also sine waves having frequencies which are integer multiples of f . Thus, if supply frequency is fifty hertz, then the third harmonic frequency is 150Hz, the fifth 250Hz, & so on.

Mesh-current analysis

The Mesh-current analysis is simply an extended application of Kirchhoff’s laws. Diagram 31.1 shows a network whose circulating currents I1, I2 and I3 have been allocated to closed loops in the circuit rather than to branches. Currents I1, I2 and I3 are referred to as mesh-currents or loop-currents. In mesh-current analysis the loop-currents are all arranged to circulate in the same direction (in diagram 31.1, shown as clockwise direction). Kirchhoff’s 2nd law is applied to each of the loops in turn, which in the circuit of diagram 31.1 generates 3 equations in three unknowns which may be solved for I1, I2 and I3.

Magneto motive force and magnetic field strength

The Magneto-motive force (mmf) is the cause due to the presence of the a magnetic flux in a magnetic circuit,

mmf,Fm=NI amperes

where N is used to represent the number of conductors (or turns) and I represents the current in amperes. We sometimes express the unit of mmf as ‘ampere-turns’. As we know, since ‘turns’ have no dimensions, the SI unit of mmf is the ampere. Magnetic field strength (or magnetizing force),

H= NI/l ampere per metre

where l stands for the mean length of the flux path in metres.

Thus mmf =NI= Hl amperes.

Bipolar junction Transistors (BJT)

The Bipolar transistors normally made up of n-p-n or p-n-p junctions of either silicon (Si) or germanium (Ge) material. These junctions are, in fact, produced in a single slice of silicon by diffusing impurities through a photo graphically reduced mask. Silicon transistors are work better when compared with germanium transistors in the wide-spread majority of applications (mainly at high levels of temperature) and thus germanium devices are very rarely encountered in modern electronic equipment.The construction of typical n-p-n and p-n-p transistors is shown in diagrams 12.1 and 12.2. For conducting the heat away from the junction (important in medium and other high-power applications) the collector is allied with the metal case of the transistor.

Linear and non-linear devices

The figure 2.3 shown below is showing a circuit. In this circuit, current I can be varied by making use of the variable resistor R2. For different setting conditions of R2, the current flowing in the resistor R1, displayed onthe ammeter, and the potential difference "p.d"across R1, displayed on the voltmeter, are noted and a graph is plotted of p.d. against the current. Diagram 2.4(a) shows the results where the straight line graph passing through the origin indicates that current is directly proportional to the p.d. Since the gradient, that is, p.d./current, is constant, resistance R1 is constant. A resistor, therefore, is a good example of a linear device.

COMMON-COLLECTOR AMPLIFIER

The common-collector amplifier shown below contains an emitter resistor but the collector is connected directly to the positive rail. The base is biased by 2 resistors. Supposing that

· the quiescent emitter current is about 1 mA,

· the voltage present across the emitter-resistor R3 is 7.5 Volt,

· bringing the output to exactly half-way between the supply rails.

· To provide for a vBE of 0.7 V, it needs to hold base at 8.2 V.

· The values of R1 and R2are calculated to provide this.

WIEN BRIDGE OSCILLATOR

The WIEN BRIDGE OSCILLATOR (figure shown below) largely relies on a pair of LR resonant networks for shifting the output signal by exactly 180 degree and one particular frequency. Then this phase-shifted signal is fed back to the non-inverting (1) input of the op amp. It is amplified and add force to the output signal. A strong sinusoidal waveform is generated. In Wien network, the two capacitors and both od the resistors are equal in value. The signal frequency is f = 1/2πRC.

The benfit of using the amplifier is that it is easily made tunable by making use of a dual ganged variable resistor for the 2 resistors in the Wien network.

PROPORTIONAL-INTEGRAL CONTROL

The proportional-integral (PI) controller make use of an integrating block to produce a signal which is integral over time of the error signal. The output value of the integrator is zero for beginning.

COLPITTS OSCILLATOR

The type of oscillator we are discussing in this tutorial largely depends on a resonant network that consists of 2 capacitors (series capacitance is equal C in total) and an inductor (L) connected in parallel with them. This L-C network resonates at a frequency, f = 1/2 π(LC)^-1/2. The op amp is wired in the circuit as an inverting amplifier with a gain of about 30. Its non-inverting (1) input is kept at half the supply voltage (1V/2) by the two 22 kΩ resistors that are acting as a potential divider. The LC network is placed in the +ve feedback loop of the op amp. At the resonant frequency level the output coming from the op amp makes the network to resonate. The tapped point between the capacitors exists at 1V/2, but the part of the oscillating signal across C2 is fed to the inverting amplifier. It is then amplified and maintains the network oscillating strongly.

Phase shift oscillator

First thing to know is that all three oscillators depend on +ve feedback to keep them oscillating. Some part of the output produced by the op amp is required to be fed back to its non-inverting input to keep itself in the oscillations.

The voltage level at the +ve terminal of the op amp is kept constant at half the supply, and stabilized by making use of capacitor.

A rising voltage at the output is fed back to the inverting inputs (2) that as a result cause a fall of output. This is +ve feedback and the op amp would have as table output. Also there is +ve feedback across the phase shift network.

HALF ADDER

HALF ADDER

Arithmetical operations are often an essential function of logic circuits. This truth table describes the simplest possible operation, adding two 1-bit binary numbers A and B:

The half adder circuit generally needs two outputs, these inputs are sum (S) and the carry-out (Co). The logic of each of these inputs is normally determined separately. Comparing the output values in the S column with those in the truth tables tells us that the operation for summing is equivalent to exclusive-OR. The operation for producing the carry-out digit is AND. The complete half adder needs only two gates. If required, the half adder can be built entirely from NAND gates by using an exclusive-OR circuit to produce S. The exclusive-OR circuit

DATA-TYPE FLIP-FLOP

Diagtam 12. 10 show the symbol used for the data-type (or D-type) flip-flop and the action of ehis flip flop is plotted in the graphs. For the purpose of clocked mode operation like this, the Set input (S) and Reset input (R) are held low. Buy there are few kinds of D-type flip-flop that do not have the R input.

12

The graphs that are shown below are drawn on the basis of a simulator, modelling a 74LS74 D-type flip-flop. This clock is running at the frequency of 10 MHz and the time scale measures in nanoseconds. When The graph lowest it shows the output Q. The simulator is stepped manually so that it enables you to make the data input high or low when we desire.

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