Configuration Of A Transistor A Transistor Can Be Configured In

Configuration of a Transistor A transistor can be configured in three ways based on the terminal which is made common to both input and output. They are common emitter, common collector and common base configurations. The characteristics of these configurations are briefly explained in the following section. Common Base Configuration: Here base is made common to both input (emitter) and output (collector. The features of the configuration can be explained with the help of characteristics. There are two types of characteristics; namely input characteristics and output characteristics. Input Characteristics: Input characteristics is plotted with input current (IE) versus input voltage (VEB) for different values of output voltage (VCB). Out Put Characteristics: The characteristics shows the variation of output current (IC) with output voltage (VCB) when input current (IE) is kept as a parameter. The transistor can be operated in three regions, namely cut off, saturation and active. Cut off region: The region for IE = 0 is called cut off region. This is a high voltage very low current region in which the transistor is perfectly OFF. Here both input and output junctions are reverse based. Saturation Region: The region to the left side of VCB = 0 is called saturation region. This is a low voltage high current region in which the transistor is perfectly ON. Here both input and output junctions are forward biased. Active Region: The remaining portion of the characteristics is the active region which is the normal region of operation of a transistor. In active region input junction is forward based and the output junction is reverse based. Common Emitter Configuration: In common emitter configuration, the emitter is made common to both input (base) and output (collector) Common Collector Configuration: In the CC configuration the collector base circuit is reverse based and the emitter is forward based with respect to the collector in the output circuit.

Basic Gates The basic operation in Boolean algebra are AND, OR and NOT. These operations can be realized using basic gates AND, Or and NOT. AND gate: Performs AND operation or MINIMUM operation which gives minimum among its inputs. It is equivalent to INTERSECTION operation in SETS. The AND operation between two inputs A and B is denoted by A.B. The truth table and the gate symbol. OR gate: It performs OR operation or MAXIMUM operation which gives maximum among its inputs. It is equivalent to UNION operation in sets. The OR operation between two inputs A and B is denoted by A + B, read as A or B. The truth table and symbol of NOT gate: IT performs NOT operation and is equivalent to complement operation in SETS. The NOT operation on any input A is denoted as A. The truth table and symbol of NOT gate. Derived Gates Basic operations in digital logic AND, OR and NOT are explained already. There are certain operations which are derived from basic operations, such as NAND, NOR, EX – OR etc. NAND gate: It is the combination of AND and NOT. NAND gate perform NAND operation. NAND gate is also called a universal gate, because all types of Boolean operations can be realized using it. NAND gate for NOT operation: If the two inputs of a NAND gate and tied together, it becomes a NOT gate. NAND gate for AND operation: Since NAND is AND followed by a NOT, complementing NAND output gives AND operation. OR using NAND: OR operation can be realized using NAND. NOR gate: It is OR gate followed by a NOT gate. The truth table and circuit symbol. Like NAND gate, NOR gate is also known as universal gate. We will illustrate how NOR can be used to realize all basic operations.

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