Bipolar Transistor Configurations

There are basically three possible ways to connect BJT in an electric circuit are:

• Common Collector Configuration
• Common Base Configuration
• Common Emitter Configuration.

Common Base Configuration

The base of transistor is grounded in common base characteristics , with the emitter acting as the input and the collector as the output. The emitter-base junction is  biased forward, whereas the junction between the collector and the base is reverse biased. Low voltage gain but high current gain is offered by the CB arrangement. It is frequently employed in impedance matching. It reverses the output signal’s phase with respect to the input and frequently utilized as a buffer between circuits with high and low impedance and in high-frequency applications like RF amplifiers.

Characteristics curves

There are two important characteristics of a transistor.

• Input characteristics- The curve drawn between emitter current and emitter – base voltage for a given value of collector – base voltage is known as input characteristics. Input characteristics of CB ΔV_CB at constant:

R_in = ΔV_BE/Δ_IE

• Output characteristics – The curve drawn between collector current and collector – base voltage, for a given value of emitter current is known as output characteristics. Output characteristics of CB ΔI_E at constant:

R_out =ΔV_CB /ΔI_B

Common Emitter Configuration

Emitter of transistor is grounded in common-emitter characteristics , and the base serves as input and the collector serves  as output. The CE configuration is like the CB configuration, it has a forward biased BE junction and a reverse biased CB junction. The voltages of CB and CE configurations are related by:

V_CE = V_CB + V_BE or, V_CB = V_CE – V_BE

and the emitter current in given by :

I_E = I_C + I_B

A CE design offers a modest current gain together with a strong voltage gain. It is frequently employed in voltage amplification. In a Phase Relationship, it Flips the  phase of input signal in relation to the output. Typically used in general-purpose amplification,  audio amplifiers and RF amplifiers .

Characteristics curves

• Input Characteristics – Input characteristics refer to the curve  between base current and base-emitter voltage for a particular collector-emitter voltage value.

• Output characteristics – The output characteristics for a given base current Ib are shown by the curve formed between collector current (Ic ) and collector-emitter voltage (Vce).

Common Collector Configuration

In the common collector characteristics, the collector of the transistor is grounded, then the base turns as input and the emitter turns as output. One voltage gain but a significant current gain is achieved with the CC setup. It serves mostly as a buffer for current. Phase Relationship: Preserves the identical phase between the signals received and sent. It include impedance transformation, impedance buffering, and voltage following to match impedance between circuits.

Characteristics curves

• Input Characteristics – To determine the i/p characteristics Vce is kept at a suitable fixed value. The base collector voltage Vbc is increased in equal steps and the corresponding increase in Ib is noted.

• Output Characteristics – The Curve drawn between emitter current and collector-emitter voltage for a given value of current is known as output characteristics. Output characteristics of CC at constant:

The term “transistor” originated in 1951 at  Bell Laboratories by  Dr. Shockley and associates. The transistor is a widely utilized essential component in modern electronic systems. Transistors generally come in two types. They are field effect transistor (FET) and BJT which is bipolar junction transistor. Signal amplification, or amplifier usage, is a common use of a BJT ( bipolar junction transistor), which is a three-terminal semiconductor device composed of combinations of p-type and n-type semiconductors. As we know this semiconductor device consists of the p-n junction and it is used or able to amplify the signal or magnify the signal. Through this the current flows and basically it contains silicon, they are also called bias resistor built-in transistors and their main objective is that -as the small current flows between the base and emitter which can control a large flow of current between the regions of collector and emitter terminals.