BJT [Bipolar Junction Transistor]

1. Configurations

1.1. Common Base

1.1.1. **Base** terminal common with Emitter and Collector

1.1.2. I/O Characteristics

1.1.2.1. Input

1.1.2.1.1. Ie increases for higher Vcb

1.1.2.2. Output

1.1.2.2.1. **Cutoff Region (Transistor OFF):** Vbe<0.7V, Ib=Ic=0

1.1.2.2.2. **Active Region (Amplification Mode):** Ic increases with Ie [Ic=αIe]

1.1.2.2.3. **Saturation Region (Fully ON - Maximum Current Flow):** Vcb=0, Ib and Ic are maximum.

1.1.2.3. Current Gain,α is ratio of Collector current (output) to Emitter current (input)​ ​

1.2. Common Emitter

1.2.1. **Emitter** terminal common with Base and Collector

1.2.2. I/O Characteristics

1.2.2.1. Input

1.2.2.1.1. Ib decreases for higher Vce, at constant Vbe

1.2.2.2. Output

1.2.2.2.1. **Cutoff Region (Transistor OFF): ** Ib=Ic=0, Vbe<0.7V

1.2.2.2.2. **Active Region (Amplification Mode):** Transistor acts as an amplifier,[Ic=βIb]

1.2.2.2.3. **Saturation Region (Fully ON - Maximum Current Flow):** Ib and Ic maximum, Vce=0

1.2.3. Current Gain,β is ratio of Collector current (output) to Base current (input)​

1.3. Common Collector

1.3.1. **Collector** terminal common with Base and Emitter

2. Transfer of Resistor- Low input current High Output current

3. TYPES

3.1. NPN

3.1.1. P region is Base and N regions are Emitter and Collector[highly doped among two]

3.2. PNP

3.2.1. N region is Base and P regions are Emitter and Collector[highly doped among two]

4. Base to Emitter Junction is always Forward Biased.

4.1. Vbe

5. Collector to Base Junction is always Reversed Biased.

5.1. Vcb

6. **Applications:** Amplification, Switching, Oscillators & Signal Generation, Voltage Regulation & Stabilization, Sensor & Control Applications, Motor Control & Power Electronics, Communication Systems