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Lecture 3

February 16, 2015

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EEE 312

Electronic Circuits

BJT AC Analysis

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COLLECTOR DC FEEDBACK CONFIGURATION

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COLLECTOR DC FEEDBACK CONFIGURATION

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COLLECTOR DC FEEDBACK CONFIGURATION

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EFFECT OF RLAND RS

The gain obtained with a source resistance in place will always be

less than that obtained under loaded or unloaded conditions due to

the drop in applied voltage across the source resistance.

For the same configuration AvNL>AvL>Avs.

For a particular design, the larger the level of RL, the greater is

the level of ac gain.

For a particular amplifier, the smaller the internal resistance of the

signal source, the greater is the overall gain.

For any network, such as those shown in Fig. 5.54 that have

coupling capacitors, the source and load resistance do not affect

the dc biasing levels.

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EFFECT OF RLAND RS

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EFFECT OF RLAND RS

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EFFECT OF RLAND RS

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EFFECT OF RLAND RSVoltage Divider

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EFFECT OF RLAND RSVoltage Divider

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EFFECT OF RLAND RSEmitter Follower

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EFFECT OF RLAND RSEmitter Follower

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For each transistor configuration, the current gain can be

determined directly from the voltage gain, the defined load, and

the input impedance.

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DETERMINING THE CURRENT GAIN

TABLE 5.1 and 5.2 (please investigate these tables)

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SUMMARY TABLES

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DARLINGTON CONNECTION

A very popular connection of two bipolar junction transistors for

operation as one super- beta transistor is the Darlington

connection shown in Figure

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DARLINGTON CONNECTION-Emitter Follower

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DC Bias

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DARLINGTON CONNECTION-Emitter Follower

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DARLINGTON CONNECTION-AC input impedance

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DARLINGTON CONNECTION-AC Current Gain

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DARLINGTON CONNECTION-AC Voltage Gain

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DARLINGTON CONNECTION-AC Voltage Gain

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DARLINGTON CONNECTION-AC Output Impedance

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DARLINGTON CONNECTION-AC Output Impedance

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DARLINGTON CONNECTION-Voltage Divider

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DC Bias

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DARLINGTON CONNECTION-Voltage Divider

AC Input Impedance

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DARLINGTON CONNECTION-Voltage Divider

AC Current Gain

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DARLINGTON CONNECTION-Voltage Divider

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FEEDBACK PAIR

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FEEDBACK PAIR

AC Operation

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FEEDBACK PAIR

AC Operation

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FEEDBACK PAIR