Chapter 7 Integrated Circuits

8/14/2019 Chapter 7 Integrated Circuits

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Q. 1 . List advantages of ICs.

Ans. IC or integrated circuits have several advantages. Some of them are

enumerated below: (i) Very small size (ii) Less weight (iii) Low cost (vi) High reliability (v) Low power consumption.

Q. 2 . List types of ICs.

Ans. On basis of fabrication techniques ICs can be classified as: (i) MonolithIc ICs (ii) Thin and thick film ICs (iii) Hybrid or multichip. On basis of chip size ICs are classified as: 1. SSI - Small Scale Integration

2. MSI-Medium Scale Integration.

3. LSI- Large Scale Integration 4. VLSI-Very Larg Scale Integration.

Q. 3 . List characteristics of ideal op-amp.

Ans. Ideal operational amplifier has following characteristics: (i) Its open loop gain isinfinite. (ii) Its input impedance is infinite. (iii) Its output impedance is zero. (iv) It has infinite frequency bandwidth.


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Q. 4 . Why cannot inductor be fabricated on an IC?

Ans. Inductors have large size and also dissipate more heat. That is whyinductors cannot b e fabricated on ICs.

Q. 5 . Give truth table for J-K flip flop.

Ans

Q. 6 . Draw and label the pin diagram of IC 741.

Ans. The IC-741 is available in 8pm and 14 pin versions we give pindiagram for 8 pin IC-741


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Q. 7 . Why an inductor cannot be fabricated on an IC?

Ans. Inductors have large size and dissipute large amount of heat that iswhy inductors cannot be of fabricated on an IC

SHORT ANSWER TYPE-QUESTIONS

Q. 1 . Give Pin diagram and its description for IC 74 XX series.

Ans. IC 74 XX series ICs are a part of TrL , (Transistor Transistor Logic)circuits. They are 14 pm ICs. These ICs have high voltage range, wide

temperature range, low power dissipation. The last two digits XX signify thelogic employed. For example: 7400 is quad 2 input NAND gate. IC 7402 isquad-2 input NOR gates, IC 7404 is a hex inverter and so on.

A general pin diagram of IC 7400 Is shown:


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Q .3 . Compare R-S flip-flop with D flip-flop.

Ans. R-S flip is a set-reset flip-flop which is used in conjunction with clockpulses to change the state of the system. D flip-flop is a delay flip which is used in conjunction with clock pulses todelay the signal output. Truth tables for clocked R-S flip-flop and D flip-flop are as shown:

R-S flip-flop

Q. 4 . What is an integrated circuit ? y is it so commonly useddiscuss?

Ans. IC or integrated circuit is a collection of number of circuit elements andcircuits on a single chip. It is a micro electronic circuit ICs are commonlyused because they possess number of advantages. Some of these areenumerated below:

1. Extremely small size


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2. Very low weight 3. Very low cost. 4. Reliability is high 5. Power consumption is low 6. Easier to replace

7. Increased speed of operation 8. Improved functional performance.

Q. 5 . Explain the terms: CMRR and output offset voltage .

Ans. CMRR is common mode rejection ratio for differential amplifier. It isdefined as ratio of differential voltage gain to common mode voltage gain.Ad CMRR= ACM CMRR is a measure of rejection of signals common to both inputs ofdifferential amplifiers. For an ideal differential amplifier, CMRR should beinfinite. Output offset voltage : With ICs it is possible to have a nearly perfect

matching between two transistors of a differential amplifier. But there existsa small difference between two transistors which gets amplified to an offsetvoltage. It is an unwanted output signal.

Q. 6 . What is a T-flip-flop ? Give its symbol.

Ans. When J & K terminals of JK flip-flop are connected together, we get a Tflip-flop. The common input terminal is called T. When high level igna1 is given asinput, output of flip-flop will toggle with every new clock pulse therebyreducing frequency at output to half of frequency of clock signal. T flip-flopcan this be considered as frequency divider. Its symbol is shown.


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Q. 7 . What is meant by IC- Timer ? How is IC-555 used to generatesquare waveform explain.

Or How is 10-555 used as frequency divider ? Explain.

Ans. IC timer is a monolithic timing circuit which can produce accurate andhighly stable time delays. IC of series 555 are used as IC timers. They canbe used to produce time delays and oscillations. IC-555 timer is eitheravailable in 8 Pin configuration on in 14 pin configuration. This IC consists of23 transistors, 2 diodes and 16 resistors. It can be used to generate squarewaveforms by using it as a free running a stable mutlivibrator. Circuit is asshown:

The external resistance RAP RB capacitance C are used to control timing ofoutput voltage (high or low). Pin connections are pin 1 is grounded ,Pin 2and 6 are shorted and connected to ground through capacitor C1 Pin 3 isoutput terminal, Pin 4 and Pin 8 are shorted and connected to Pin 5 has abypass capacitor C1 Pin 7 is connected to Pin 6 through a resistance.


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Pin diagram below is shown below

Q. 8 . What are limitations of ICs?

Ans. The following are limitations of ICs: (1) If one component fails, whole IC needs to be replaced. (ii) Their power rating is low.

(iii) We need to connect inductors and transformers externally. (iv) They have low operating voltages. (v) The resistances and capacitances are voltage dependent.

Q. 9 . Give Pin diagram and discription of 10741.

Ans. 1C-741 is one o the most versatile and widely used members ofoperational.amplifier family. It is basically an 8-pin IC, whose pin diagram and

description is given below:


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The first stage is a double ended high gain differential amplifier with a

constant source to increase CMRR. It determines input resistance of IC.Second stage is intermediate stage which is also a differential ampliferdriven by output from first stage. It has high gain.Third stage is levelshifting stage which is a emitter follower circuit. It is used to shift d.c. levelat output of second stageto zero volts w.r.t. ground. It helps to maintainoperating point of succeeding stage Fourth stage is output stage. It usuallyconsists of a push pull amplifier which is used to increase output voltage andcurrent capability of amplifier. It has low output resistance.

Q. 10. What are flip-flops ? How are invertors used to represent R-.Sflip-flops ? Discuss.


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Ans. A flip-flop is a bistable multivibrator having two stable states. It isbasic memory element.. One of the stable states is called SET and other isRESET or clear. It normally has two inputs and two outputs. The outputs arecomplementary. in addition to inputs, a flip- flop has a clock terminal which

has a train of pulses applied to it. The state of output at any instant dependson past outputs and data inputs present at that instant of time. The statecan be changed only when clock pulse is applied. Two inverting transistorscan represent R-S flip-flop. This is as shown:

Here one of the transistors works in saturation region and other is cut offregion (inverse of saturation).

Q. 11 . What are integrated circuits ? What are its advantages overdiscrete components?

Ans. Integrated circuits are an assembly of number of circuits on a singlechip of standard size. The advantages of integrated circuits over discretecomponents are:

(i) Complex circuitry and connections involved while using discretecomponents avoided. (ii) Size of circuits becomes smaller. (iii). Efficiency of such circuits is more. (iv) They consume low power (v) They have high operating speeds.


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Q. 12 . Draw the circuit of JK flip flop and explain its worldng withhelp of truth table?

Ans. The circuit for the flip flop is as shown:

When clock pulse is high then only output is available. For low clock input,no output is available. When J and K input are both low, output is theprevious stage. When J is low and K is high, itis reset When J is high K islow, it is set when both J and K are high then flip flop will toggle. The waveform is as shown:


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Q. 13 What is the need of voltage regulator in a power supply ?Discuss the applications of voltage regulator IC 7805.

Ans. Voltage regulators are required in a power supply in order to givespecific value of voltage. Also, voltage regulators can provide positive ornegative biased voltages. Voltage regulators have features such asprogrammable output, facility to boost output voltage or current internalprotection such as thermal short down, floating to facilitate higher outputvoltage etc. Since they are small in size they reduce size of power supplyand power supply design becomes quick and easy.

IC 7805 voltage regulator is a fixed voltage regulator. It is a positive voltageregulator having three terminals. It gives regulated supply of +5V DC forTTL logic circuits. It is also used in electronic circuits where +5V regulatedsupply is required such as with micro controller etc.

Chapter 7 Integrated Circuits

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