Input offset voltage

Inspite of all the compensation techniques the output voltage is still not zero with zero input voltage.  Hence a small voltage is applied at the input terminals to make output voltage zero which is called as input offset voltage. The following are the non-inverting and inverting amplifiers respectively: Where  V1 =0 gives Voltage V2 is given by    V2 = V0 [R1/(R1+ Rf)] Or  V0 = V2 [ (R1+ Rf)/ R1] Since, Vios = │V1 – V2│and Vi = 0 Vios = │0 – V2│ =  V2 V0 = [1+(Rf/R1)] Vios...
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Input Offset Current

It is the difference between the current flowing from inverting and non-inverting currents of an op-amp.              Ios = IB+ - IB-   With bias current compensation the offset current will produce an output voltage when the input voltage is zero We have,           V1 =IB+ Rcomp             And   I1 = V1/R1 KCL at node ‘a’ gives            I2 = (IB- - I1)               = IB- [IB+ (Rcomp/R1)] Also,                 V0 = I2 Rf - V1           V0 = I2 Rf - IB+ Rcomp              = [IB- - IB+Rcomp]Rf - IB+Rcomp We know, Rcomp = R1Rf / R1+Rf Substituting Rcomp, we have,         V0 = Rf [IB- - IB+] The effect of offset current can be minimized by keeping feedback resistance value be small  ...
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Characteristics of Op-amp

The non- ideal characteristics of op-amp which are DC and AC are:DC error components are:input bias current input offset current input offset voltage thermal driftInput Bias Current:The input bias current of an operational amplifier is the average of the two currents flowing at the inverting and non-inverting terminal respectively. The mathematical equation is given by:         IB = (IB++IB-)/2 For a Basic inverting op-amp : basic inverting op-amp If V1 = 0, then output voltage is offset given by,                V0 = IB - Rf1For 741 op-amp, Rf  = 1mΩ and input bias current is 500mA or less.Therefore, output voltage is driven to 500mV.In applications where signal levels are measure in milli-volts it is totally unacceptable. Hence, a compensated resistor is added between non-inverting input terminal and ground. Current IB+ going through the compensator resistor has a voltage V1 across itFrom KVL,-V1 + 0 + V2 – V0 = 0By selecting proper value of Rcomp V2 and be cancelled with V1 to make V0 Therefore, V1...
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Management

Management is getting the work done through the efforts of other people it is necessary to guide, direct, coordinating and controlling human efforts towards the fulfillment of the organization. The goals of the organization are fulfilled through the use of resource lke men, material, machines and money etc.                Management is a social process refer to the series of actives that are performed in the society. This activities are performed by administrators, politicians, economists, housewives, parents, doctors, lawyers etc. The following are features of management: Management also denotes a body of people involved in decision making. Management is omnipresent and universal. Management is profession. Management is inter disciplinary. Management has Four types of resource i.e, Men, Material, Money, Machines. Management is situational in nature. Scope of Management: This is the end result after preliminary scope statement is refined this is classified into 8 types: Financial Management. Personal Management. Purchasing Management. Production Management. Maintenance Management. Transport Management. Office...
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Introduction to Management

Management:According to Henry Fayol (1916) the management is to forecast, plan to organize, to control, to coordinate, to command.                                                                                (OR)According to Peter F Ducker (1955) management is concerned with the systematic organization of economic resources and it's take to make the resource and its task is to make this resources productive.                                                                                (OR)According to E. F. L. Brech (1957) management is a social process that consists of planning and control, coordination, and motivation is called motivation....
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Conditions of an Ideal Operational Amplifier

An op-amp is said to be ideal if it has the following characteristics. Open loop voltage gain (AOL) is infinity. Input resistance (Ri) is infinity. Output resistance (Ro) is zero. Bandwidth (BW) is infinity. Zero off-set (i.e) V0 = 0, when V1 = 0 & V2 = 0. An ideal op-amp cross no current and both the input terminal i 1 = i2 = 0. Because gain is infinite the voltage between inverting and non-inverting terminals i.e op-amp is essentially zero for infinite output voltage V0 is independent of the current drawn from the output is R0 = 0....
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Parameters of Op-amp

Input off set voltage :  It is a voltage that must be applied between the two input terminals of an op-amp to null the output. Input off-set current : The algebraic difference difference between the currents in the inverting and non- inverting currents. Typical value of input offset current is 200 nAmp. Iiv = │I­B1 – IB2│ Input bias current : It is the average of the currents that flow into inverting and non-inverting currents of op-amp.IC is typically 500 nAmp maximum for IC741.Differential Input Resistance : It is denoted by R i    It is an equivalent resistance that can be measured inverting or non-inverting with the other terminal grounded. Input Capacitance (Ci) : It is the equivalent capacitance that can be measure in that act as inverting and non-inverting terminal with the other terminal being grounded. It is typically 1.4 Farads. Common Mode Voltage: It is the operating voltage in common mode operation, when some voltage is being applied to both the input terminals. Common Mode Rejection Ratio: It is a ratio of differential voltage gain...
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Model of Digital Communication system – Channel Encoder and decoder

Channel encoder and decoder : Channel Encoder :After converting message or information signal in the form of binary sequence by the source encoder, the signal is transmitted to the channel. The channel acts as noise and interference to signal being transmitted. Therefore, errors are introduced in the binary sequence received at the receiver. To avoid these errors channel encoding is done. The channel encoder acts as some redundant binary bits to the input sequence.      Example: The code word from the source encoder is 3- bits long and one redundant bit is added in channel encoder. If it an even parity then the number of 1's in the encoded word remain even. At the receiver if odd number of 1's are detected then reciver comes to know that there is an error in the receiver signal.Channel Decoder :The channel decoder is able to detect errors in the bit sequence and reduce the effects of channel noise interference. The extra bits/...
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Elements of Digital Communication:

Model Digital Communication System :      The purpose of this system is to transmit the message or square of symbols coming out of the source to a destination point.      The source and destination points are separated through a communication channel Model of Digital communication system * Discrete information source : The information source generates the message signal to be transmitted an analof information source may be transformed into a discrete information source through the process of sampling and quantization. The discrete information sources are charectarized by the following Parameters:  Source : These are the letter, digits or special charectar available in the information source. Source Alphabet Probability : Each source alphabet  from information source has independent occurrence rate in the sequence.Example: Letter or words (a, e, i, o, u) occurs frequently in the source. Symbol Rate: It is the rate at which the information source generates source alphabet and represented in symbol/ sec unit. Information Rate: This parameter defines the average information content of the symbols. Entropy...
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Manufacturers Designation For Linear ICs

Each manufacturer uses a specific code & assigns a specific type of number to the ICs produced. The following are the codes for different manufactures of ICs:  IC741 - op. amp Fairchild - uA, uA7 National Semiconductors - LM, LH, LF, TBA Motorola - MC, MFC RCA - CA, CD Texas Instruments - SN Signetics - N/S, NE/SE Burr_Brown - BB Ideal and Practical op-amp's : Ideal Operational Amplifiers : Inverting amplifier : this amplifier has non-inverting terminal ground and input is applied to the inverting terminal through a resistive network. The figure shows the circuit of an inverting amplifier: Inverting Circuit As, V_d= 0, node 'a' is at ground potential for an ideal op-amp             therefore, i_1, through R_1 is i_1= V_1/R_1 Op-amp draws no current and V_o= -i_1*R_f= -V_i* R_f/R_1             therefore, gain of amp closed loop gain (A_(cl) = V_0/V_i = -v_i R_f/R_i                              ...
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