what is asynchronous(ripple) counters,synchronous counters, what is register , discrete components, transistors switches full tutorial|

counter

The counter is a circuit with a set of flip-flops which counts the number of pulse given at the clock input.At any time the number of pulse recieved (count value) is shown in the counter output, the output pattern in the flip-flops in different state. the number of flip-flops used and how they are connected determine the number of states and the sequence of the state the counter goes through in each complete cycle.  counters can be classified into two broad categories according to the way the are clocked 

1. Asynchronous (ripple) counters-the first flip-flop is clocked by the external clock pulse, and then each successive flip-flop is clocked by the Q or Q' output of the previous flip-flop.
2. synchronous counters-all memory elements are simultaneously triggered by the same clock.

Asynchronous (Ripple ) Counters

A two-bit asynchronous counter is shown in adjoining figure. the external clock is connected to the clock input of the first flip-flop (FF0) only. so,  FF0  changes state at the falling edge of each clock pulse, but FF1  changes only when triggered by the falling edge of the Q output of FF0 . because of the inherent propagation delay through a flip-flop, the transition of the input  clock pulse and a transition of the Q  output of FF0  can never occur at exactly the same time. therefore , the flip-flops cannot be triggered simultaneously, producing an asynchronous operation.

Usually, all the CLEAR inputs are connected together, so that a single pulse can clear all the flip-flops before counting starts. the clock pulse fed into FF0  is rippled through the other counters after propagation delays, like a ripple on water, hence the name ripple counter.

synchronous counters

In synchronous counters, the clock inputs of all the flip-flops are connected together and are triggered by the input pulse thus, all the flip-flops changes state simultaneously (in parallel). the circuit below is a 3-bit synchronous counter. the and K inputs of FF0 are connected to HIGH. FF1  has its and K inputs connedted to the output of FF0,  and the and K inputs of FF2 are connected to the output of an AND  gate that is fed by the outputs of FF0 and FF1.

The most important advantage of synchronous counters is that there is no cumulative time delay because all flip-flops are triggered in parallel. thus, the maximum operating frequency for this counter will be significantly higher than for the corresponding ripple counters. 

Register

A register has multiple flip-flops with a common triggered clock input. for a four bit register implies that four flip-flops are connected in parallel with their clock inputs sorted. in addition, the CLR  input of the individual flop-flops can be sorted together forming a common RESET  input. A basic four-bit shift register can be constructed using four D  flip-flops, as shown below. thr operation of the circuit is as follow. the register is first cleared, forcing all four outputs to zero. the input data is then applied sequentially to the D  input of the first flip-flop on the left (FF0).during each clock pulse, one bit is transmitted from left to right. assume a data word to be 1001. the least significant bit of the data has to be shifted through the register from FF0 to FF3.

Shift register are a type of sequential logic circuit, mainly for storage of digital data. they are a group of flip-flops connected in a chain so that the output from one flip-flop becomes the input of the next flip-flop. most of the registers  possess no characteristic internal sequence of state. all the flip-flops are driven by a common clock, and all are set or reset simultaneously.

there are five basic types of shift register such as:

1. serial in-serial out.
2. serial in-parallel out.
3. parallel in-serial out.
4. parallel in -parallel out.
5. bi-directional shift registers.

Discrete Components

Capacitors are rated in farads. they are represented by "C" or "F" , depending upon the context. because by nature, capacitors are so small, they are usually rated in even smaller units of farads. they are:

Mf:Milli-Farad,1*10^-3 Farad (1000^th of a farad)

Uf: Micro-Farad, 1*10^-6  farad (1,000,000^th of a farad)

mF: Micro-Farad

ufd: Micro-Farad

mfd( or MFD) d, 1*10^-9 Farad (1,000,000,000 th of a Farad)- Common everywhere except the US

Pf: Pico –Farad,

Nf: Nano-Fara

1* mmF:  Micro-Micro-Farad

10^-12 Farad (1,000,000,000 ,000 th of a Farad

the most commonly used items are noted in bold. all else is practically non-existent. look up your local vendor for typical descriptions. here is an overview of most common capacitor types:

1. Ceramic: Fairly cheap but not available in really high capacitances - 2uF-10uF are about the max for any practical devices. surface mount devices have essentially no series inductance and are commonly used to bypass high-frequency noise away from digital IC's. not polarized .
2. Electrolytic: Cheapest capacitance per dollar. mostly used for 'bulk' power supply. typical values 1 uF-5000+uF. polarized. Fairly durable, but will literally explode if reverse-biased. tolerances of ±10% and  ±20% are not uncommon. A tolerance of +80% and -20%  is common for capacitors used in power supplies.
3. Tantalum: Expensive capacitors. very high capacitance values available. polarized.
4. Polyester/plastic Film: Kind of expensive, not very high capacitance values. polyester capacitors have very very stable temperature characteristics (capacitance change is very small as temperature changes). Used where stable capacitance is important like oscillators and timers.  NOT  polarized. 

Diodes let electrons flow through them only in one direction. diodes flow from cathode to anode. the cathode side of the diode is marked with a band around it. there are three types of diodes: diodes, zener diodes and LED .

Zener diodes have a set voltage rating. when a voltage exceeds the voltage rating going in the opposite direction ( from anode to cathode) , the diode allows the electrons flow.

Light Emitting diodes (LED  for short) are just like the regular diodes except that it lights up when electrons are flowing through . Note: there are't any bands to identify which pin is anode and which is cathode. However, one pin is longer then the other. the longer pin is the anode, the positive side.

Resistors are electronic components used extensively on the circuit boards of electronic equipment. Resis-tors are usually used to limit current, attenuate signals, dissipate power(heating) or to terminate signal lines. 

Resistors are usually color code (see cart A) with stripes to reveal their resistance value (in ohms) as well as their manufacturing tolerance. Most important characteristics of resistors are the resistance, tolerance and voltage. 

The tolerance bands indicates the accuracy of the values. A 5%  tolerance (gold band) for example, indicates that the resistor will be within 5% of its value. for most applications, a resistor within 5% tolerance should be sufficient. to get the value of a resistor, hold the resistor so that the tolerance band is on the right. the first two color bands from the left are the significant figures-simply write down

The number presented by the colors. the third band is the multiplier- it tells you how many zeros to put after the significant figures. put them all together and you have the value.

here are the following different resistor types. 

Carbon film resistor:cheap general purpose resistor, works quite well also on high frequencies, resistance is somewhat dependent on the voltage over resistor( does not generally have effect in practice )

Composite resistor: Usually some medium power resistors are built in this way. has low inductance, large capacitance, poor temperature stability, noisy and not very good long time stability. composite resistor can handle well short overload surges.
Metal film resistor: good temperature stability, good long time stability, cannot handle overloads well.
Metal oxide resister: mostly similar  features metal film resistor but better surge handling capacity , higher temperature rating them metal film resistor, low voltage dependability, low noise better for RF  than wire would resistor but usually worse temperature stability.
Thick film resistor: similar properties as metal film resistor but can handle surges better, can withstand high temperatures.
 Thin film resistor: used mainly for high power resistors, can be made accurate for measuring circuits, high inductance because it consists of wound wire.
Inductors  are your basic components . these are the last of the purely passive components. An inductor is most commonly a coil but in reality, even a straight piece of wire has inductance. winding it into a coil simply concentrates the magnetic field and increases the inductance considerable for a given length of wire. Although there are some very common inductive components ( such as transformers, amplifiers to prevent instability with capacitive loads.

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