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- Digital Electronics Circuit - DEC
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**Veer Surendra Sai University Of Technology VSSUT -**- Electrical Engineering
- B.Tech
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ELECTRONICS CIRCUITS (3-1-0) MODULE-I Diode circuit: Load line concept, clipping circuits, comparators, sampling gate, rectifiers, capacitive filters, additional diode circuit. Transistor: the junction transistor, transistor as an amplifier, transistor construction, the CE configuration, the CB configuration, the CE cut-off and saturation region, common emitter current gain, the common collector configuration, analytical expression for transistor characteristics, the phototransistor. Transistor at low frequency: Graphical analysis of the CE model, two-port model and hybrid model, transistor hybrid model, the h-parameter, analysis of transistor amplifier circuit using hparameter, the emitter follower, miller’s theorem and its duality, cascading transistor amplifiers, simplified CE and CC configuration. MODULE-II (10 Lectures) Junction FET and its V-I characteristics, FET small signal model, FET biasing, MOSFET, FET as a voltage-variable resistor (VVR), CD amplifier, the hybrid-pi CE transistor model, hybrid-pi conductance and capacitance, validity of hybrid-pi model, variation of hybrid-pi parameters, the CE short-circuit current gain, current gain with resistive load, single stage CE transistor amplifier response, emitter follower at high frequency. Classification of amplifier, distortion in amplifier, frequency response of amplifier, bode plots, step response of amplifier, band pass of cascade stages, the RC coupled amplifier, high frequency response of two cascaded CE transistor stages. MODULE-III (10 Lectures) Classification of amplifier, feedback concept, transfer gain, negative feedback, input-output resistance, method of analysis of a feedback amplifier, voltage- series, voltage-shunt, currentseries and current shunt feedback, effect of feedback on bandwidth, double and three pole transfer function with feedback, approximation analysis of multi-pole feedback, voltage-series, voltage-shunt, current- series and current-shunt frequency response, stability, gain and phase margin, compensation, different type of oscillator, frequency stability. MODULE-IV (10 Lectures) The basic operational amplifier (OPAMP), differential amplifier and its transfer characteristics, emitter coupled differential amplifier, IC-OPAMP, offset error voltage and current, temperature drift of input offset voltage and current, measurement of OPAMP parameter and its frequency response, different type of OPAMP compensation and its step response. Basic OPAMP application, differential DC amplifier, AC amplifier, analog integrator and differentiator, active filter, resonant band-pass filter, delay equalizer, comparators, sample-hold circuit, AC/DC convertors, logarithmic amplifier, Schmitt trigger, ECL, TTL and 555-timer. BOOKS: 1. Millma. J. and Halkias .C. Integrated Electronics, TMH, 2007. 2. S. Salivahanan, N. Suresh Kumar and A. Vallavaraj, Electronic Devices and Circuits, 2nd Edition, TMH, 2007. 3. Robert L. Boylestad and Louis Nashelsky, Electronic Devices and Circuit Theory, 9th Edition, Pearson Education / PHI, 2007.

CHAPTER-1 (Lecture-1 & 2) 1.1The The Diode as a Circuit Element Diodes are referred to as non-linear linear circuit elements because of the diode characteristic curve i.e. = ( -1) 1) ...(1.1) Where =reverse saturation current in the range of pA for low-power low power diode. = is thermal voltage(about 26 mV at room ttemperature, emperature, T = 300 K). =ideality factor(1< <2). Figure 1.1: a) Circuit symbol for a diode and b) current current versus voltage for a semiconductor diode. For most applications the non-linear non linear region can be avoided and the device can be modeled by piece-wise wise linear circuit elements. Qualitatively we can just think of an ideal diode has having two regions: a conduction region of zero resistance and an infinite resistance non-conduction non region. For many circuit applications, this ideal diode diode model is an adequate representation of an actual diode and simply requires that the circuit analysis be separated into two parts: forward

current and reverse current. Figure 1.1 shows a schematic symbol for a diode and the currentvoltage curve for an ideal diode. Figure 1.1: a) Schematic symbol for a diode and b) current versus voltage for an ideal diode. A diode can more accurately be described using the equivalent circuit model shown in figure 1.2. ) in series with a If a diode is forward biased with a high voltage it acts like a resistor ( voltage source ( ). For reverse biasing, it acts simply as a resistor ( ). These approximations are referred to as the linear element model of a diode. Figure 1.2: Equivalent circuit model of a junction diode. 1.2 Load line concept of Diode: The applied load will normally have an important impact on the behavior of a device. If the analysis is performed in a graphical manner, a line can be drawn on the characteristics of the device that represents the applied load. The intersection of the load line with the characteristics will determine the point of operation of the system. Such an analysis is called load-line analysis. Consider the network of Fig. 1.2 using a diode having diode voltage , resistor R and a voltage source . Due to the voltage source a current is established through a series circuit in clock wise manner. The current direction and the defined direction of conduction of the diode is matched so the diode is in the “on” state and conduction has been established.

(a) (b) Figure 2.1: Series diode configuration (a) circuit (b)) characteristics. characteristics Applying Kirchhoff’s voltage law to the series circuit of Fig. 2.1 will result in -R - =0 =R ...(2.1) The intersections of the load line on the characteristics can easily be determined if one simply employs the fact that anywhere on the horizontal axis =00 A and anywhere on the vertical axis = 0 V. when =0 , then the above equation will be =0+R = ...(2.2) Similarly when = = =0, then the equation 2.1 will be + (0A) R | ...(2.3)

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