Hardware & Software System

A transistor amplifier must satisfy three basic conditions, namely :   1) proper zero signal collector current.   2) proper base-emitter voltage at any instant and   3) proper collector-emitter voltage at any instant. It is the fulfilment of these conditions which is known as transistor biasing.          The proper flow of zero signal collector current and the maintenance of proper collector-emitter voltage during the passage of signal is known as transistor biasing.

The basic function of transistor is to do amplification.The weak signal is given to the base transistor and amplified output is obtained in the collector circuit. One important requirement during amplification is that only the magnitude of the signal should increase and there should be no change in signal shape. this increase is magnitude of the signal without any change in shape is known as faithful amplification . In order to achieve this,means are provided to ensure that input circuit of the transistor remains forward biased and output circuit always remains reverse biased during all parts of the signal. This is known as transistor biasing.

A pn junction is known as a semi-conductor or * crystal diode .                The outstanding property of a crystal diode to conduct current in one direction only permits it to be used as rectifier. A crystal diode is usually represented by the schematic symbol shown in fig 1. The arrow in the symbol indicates the direction of easier conventional current flow. fig. 1      A crystal diode has two terminals. When it bis     connected in a circuit one thing to decide is         whether the diode is forward or reverse biased.     There is an easy rule to ascertain it. If thew external circuit is trying to push the conventional current in the direction of arrow, the diode is forward biased. On the other hand, if the conventional current is trying to flow opposite to arrowhead, the diode is reverse biased. Putting on the simple words :         1) If a...

 Logical 1 and 0 are generally represented by voltage level. In a positive logic system, the most Positive voltage system (HIGH) represents the logical 1 status, and the most Negative voltage level (LOW) represents the logical 0 state. In a Negative logic system, the most Positive (HIGH) voltage level represents logical 0 state and the most Negative (LOW) voltage level represents logical 1 state. For example, if the voltage level are -0.1 and -5 V, then in a positive logic system the -5 V level represents a 0 state and the -0.1 level represents a 1 state; in a negative logic system, -0.1 level represents a 0 state and -5 V represents a 1 state. Conversely, if the voltage level are 0.1 V and 5 V, then in a positive logic system the 5 V level represents a 1 state and the 0.1 V represents a 0 state; in a negative logic system, the 0.1 V represents a 1 state and the 5 V level represents a 0 state.                       The effec...

Boolean Addition :- Addition by the Boolean method involves variables having values of either a binary 1 or a 0. The basic rules of Boolean addition are given bellow.                                                                                                    0+0=0                                                        0+1=1                                                        1+0=1                   ...

Logical operation can be expressed and minimized mathematically using the rules, laws, and theorems of Boolean algebra. It is a convenient and systematic method of expressing and analyzing the operation of digital circuit and system. Boolean algebra used binary arithmetic variables which have two distinct symbols 0 and 1. These are called levels or states of logic. For example, a binary 1 represents a High level and a binary 0 represent a Low level.

The logical inverse operation converts the logical 1 to the logical 0 and vice versa. This method is also called the NOT operation. The symbol used for this operation is a bar over the function or the variable. Several notations, such as adding an asterisk, a star, prime, etc. over the variable, are used to indicate the NOT operation. "NOT A" or the complement of A is represented by A bar.