Common Emitter Configuration and Collector Curve

It Describe Common Emitter Configuration Behavior.

1. Developed By: Zeeshan Rafiq

2. bjt Common Emitter & Collector Curve Presentation Topic :- Group Members:- Zeeshan Rafique (16201519-026) Muhammad Abbas ( 16201519-001) Muhammad Umar ( 16201519-099) Zaid Khalid ( 16201519-106) Developed By: Zeeshan Rafiq

3. Common emitter It is called common-emitter configuration since : - emitter is common or reference to both input and output terminals. - emitter is usually the terminal closest to or at ground potential . Almost amplifier design is using connection of CE due to the high gain for current and voltage . Two set of characteristics are necessary to describe the behavior for CE ;input (base terminal) and output (collector terminal) parameters . This circuit has two loops. The Left Loop is the base loop & the right loop is the collector loop. Note: The current relation are still applicable I E =I C +I B & I C = b I B Developed By: Zeeshan Rafiq

4. Input characteristics:- Input takes the form of a forward biased pn junction. Input characteristics are therefore similar to those of a semiconductor diode. Output Characteristics:- Input characteristics Graph The magnitude of I B in micro ampere and not as horizontal as I E in common-base circuit. The output set relates an output current I C to an output voltage V CE for various level of input current I B. There are three portions as shown in Next Slides:- Developed By: Zeeshan Rafiq

5. Common emitter Active Region: The active region, located at upper-right quadrant, has the greatest linearity.() The curve for IB are nearly straight and equally spaced. In active Region, B-E junction is forward Biased.. Cutoff Region The region below I B =0UA is defined as cutoff region. Saturation Region The small portion near the ordinate, is the saturation region, which should be avoided for linear amplification In the dc mode, the level of I C and I B at the operation point are related by: Normally B ranges from 40 to 400 Active Region Saturation region Cutoff region Collector output Graph Developed By: Zeeshan Rafiq

6. Common Emitter Configuration (Base Biases) In the base loop, the V BB source biased the emitter diode with R B as a current limiting resistance. By changing V BB or R B ,we can change the base current. So base current will change the collector current. It means that small current(BASE) will produce large current (Collector). In the collector loop, a source voltage V CC reverse biases the collector diode through R C . Double scripts notation is used with transistor circuit. When the subscript is same, represent a source(V CC )(V BB ) Single scripts are used for node voltages, that is, voltages between the subscript point and ground(reference). In CE (BaseBiase) Connection, dc current gain beta exist which can be change overall output. By applying simple KVL, we can find Output Voltages At input side: I B = V BB - V BE R B Now at Output side: V CE =V CC -I C R C & .’. I C =BI B Developed By: Zeeshan Rafiq

7. Current Gain Beta dependency:- Itself transistor Collector Current Temperature Due to Beta dependency in Base Bias we avoid some case to use in it amplifier circuit. So we use another configuration. Developed By: Zeeshan Rafiq

8. Common Emitter Configuration (Emitter Bias) Digital circuits are the type of circuits used in computers. In this area, Base bias and circuits derived from base bias are useful. But when it comes to amplifiers, we need circuits whose Q points are immune to changes in current gain. As you can see, the resistor moved from base circuit to the emitter circuit. That one make change all over the world. Q point have greater less effect due to current gain BASIC IDEA B ase supply voltage directly applied to base and trouble shooter will read V BB B\W Base and Ground. Now emitter is above the ground and has a voltage given by: V E =V BB -V BE I E =( V BB -V BE ) R E Now we Find Collector Voltage By KVL at output side V CE =V CC -I C (R C +R E ) I E = ~ I C I C =( V BB -V BE ) R E We can draw from this formula a load line Developed By: Zeeshan Rafiq

9. Minor effect of Current Gain factor This current gain has minor effect on the collector current. Under applying all operating conditions, the three currents are related by: I E =I C +I B Which can be rearranged as: I E =I C +(I C +I C / B dc ) Developed By: Zeeshan Rafiq

10. Collector Curve This set of curves is also called a family of curves. When V CE is zero, the collector diode is not reverse bias. This is why, graph shows a collector current of zero when V CE is zero. When V CE is increasing from Zero, the collector current rises sharply. When V CE is few tenths of a volts, the collector current becomes almost constant and equal to 1mA. Developed By: Zeeshan Rafiq

11. Thank You Jazak ALLAH