Explain the function of sample and hold circuit by using op-amp.

1 Answer

Answer :

sample and hold circuit by using op-amp

image

The n-channel MOSFET is driven by a control voltage VC acts as a switch. The control voltage VC is applied to the gate of the MOSFET. The circuit diagram can be split into three stages. First stage is the voltage follower second one is the switch and capacitor and the third one is a gain the voltage follower. When VC is high the MOSFET turns on and acts like a closed switch .This is sampling mode .The capacitor charges through the MOSFET to the instantaneous input voltage. As soon as VC=0 the MOSFET turns off and the capacitor is disconnected from OPMP1 output. Capacitor cannot discharge through amplifier A2 due to its high impedance. Thus this is the hold mode in which the capacitor holds the latest sample value. The time period during which the voltage across capacitor is equal to input voltage is called sample period. The time period during which the voltage across capacitor is constant is called Hold period.

Related questions

Description : Describe how Op-Amp is used as adder using circuit diagram and output voltage equation.

Last Answer : Summing Amplifier Circuit In this simple summing amplifier circuit, the output voltage, ( Vout ) now becomes proportional to the sum of the input voltages, V1, V2, V3, etc. Then we can ... to the non-inverting input of the op-amp, it will produce the positive sum of the input voltages.

Last Answer : A non inverting closed loop op amp circuit generally has a gain factor Greater than one.

Description : Draw the diagram of zero crossing detector using op-amp and explain its working.

Last Answer : The zero crossing detector circuit is an important application of the op-amp comparator circuit. It can also be called as the sine to square wave converter. Anyone of the inverting or non-inverting ... the possibility of any false zero crossing due to noise voltages at the op-amp input.

Description : Write transfer function of op amp as an integer.

Last Answer : The transfer function of the integer is  LAL=1/MR1cf

Description : Draw and explain the Op-amp based subtractor

Last Answer : Working The subtractor circuit is a basic op-amp circuit whose output voltage is the difference between two input voltages.  In the above circuit, the two input voltages are V1 and V2.  The op amp is used ... When differential gain is 1, ie Rf = R,  the output voltage is Vo = (V2 - V1).

Description : What is Op -Amp ?

Last Answer : The operational amplifier is abbreviated as OP-Amp . This OP-Amp is a high gain direct coupled negative feedback amplifier circuit with multiple transistors. Op-Amp is a modular , multistage amplifying device with a ... of op-amp is 500 ml. Op-amp IC : A709, LM108, LM208, CA741 and CA741T.

Description : What is op amp?

Last Answer : An operational amplifier, which is often called an op-amp, is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output.[1] An op-amp ... at the input terminals (ideally infinite) and low output impedance at the output terminal(s) (idea

Description : What is op amp?

Last Answer : An operational amplifier, which is often called an op-amp, is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output.[1] An op-amp ... at the input terminals (ideally infinite) and low output impedance at the output terminal(s) (idea

Description : What is the type of feedback used in an op-amp Schmitt trigger?

Last Answer : The type of feedback used in an op-amp Schmitt trigger is positive feedback.

Description : What is the basic building block of an op-amp?

Last Answer : The basic building block of an op-amp is differential amplifier.

Description : What is the type of feedback employed in the inverting op-amp amplifier?

Last Answer : Negative feedback is employed in the inverting op-amp amplifier.

Description : What are the DC characteristics of an op-amp?

Last Answer : a. input bias current b. Input offset current c .Input offset voltage d. Thermal drift

Description : What are the AC characteristics of an op-amp?

Last Answer : a. Frequency response b. Slew rate

Description : What is compensated op-amp?

Last Answer : Op-amp, which uses a capacitor internally for compensation, is called a compensated op-amp. This op-amp has a high gain stability and low bandwidth.

Description : What is an op-amp?

Last Answer : The operational amplifier is a multi-terminal device, which is quite complex internally. An operational amplifier is a direct coupled high gain amplifier usually consisting of one or more ... as well as ac input signals and was originally designed for computing such mathematical functions.

Description : Coil of relay is connected to the A. input of op-amp B. output of op-amp C. midpoint of op-am D. anywhere in between input and ouput of op-amp

Last Answer : output of op-amp

Description : Actual op-amp may have an open loop gain of A. 102 B. 105 C. 103 D. 104

Last Answer : 105

Description : If current of 20 mA is passing through op-amp and voltage drop across series resistor is 10 V then value of resistance is A. 500Ω B. 400Ω C. 300Ω D. 200Ω

Last Answer : 500Ω

Description : As long as op-amp is not saturated, the potential difference between inverting and non-inverting inputs is A. zero B. infinite C. 1 D. 2

Last Answer : zero

Description :  A device used to avoid the relay destroying the op-amp is A. diode B. LED C. reverse bias diode D. forward biased diode

Last Answer : reverse bias diode

Description : Number of power supplies required to get output of op-amp is A. two B. four C. six D. three

Last Answer : two

Description : Impedance of ideal op-amp is A. zero B. 1 C. infinite D. 2

Last Answer :  infinite

Description : Output resistance of an actual op-amp is A. 45Ω B. 46Ω C. 70Ω D. 75Ω

Last Answer : 75Ω

Description : Op-amp can provide maximum output current of A. 25 mAB. 30 mA C. 35 mA D. 40 mA

Last Answer :  25 mA

Description : What are the areas of application of non-linear op- amp circuits?

Last Answer : 1. Industrial instrumentation 2. Communication 3. Signal processing

Description : Define CMRR of an op-amp.

Last Answer : The relative sensitivity of an op-amp to a difference signal as compared to a common – mode signal is called the common –mode rejection ratio. It is expressed in decibels. CMRR= Ad/Ac

Description : Define input offset current. State the reasons for the offset currents at the input of the op-amp.

Last Answer : The difference between the bias currents at the input terminals of the op-amp is called as input offset current. The input terminals conduct a small value of dc current to bias the input transistors.Since the input transistors cannot be made identical,there exists a difference in bias currents.

Description : Define virtual ground of a OP-Amp? 

Last Answer : A virtual ground is a ground which acts like a ground. It is a point that is at the fixed ground potential (0v),though it is not practically connected to the actual ground or common terminal of the circuit.

Description : Why open loop OP-AMP configurations are not used in linear applications?

Last Answer : The open loop gain of the op-amp is not a constant and it varies with changing the temperature and variations in power supply.Also the bandwidth of the open loop op-amp is negligibly small.For this reasons open loop OP-AMP configurations are not used in linear applications.

Description : what is meant by virtual ground in the op amp ?

Last Answer : Ans-The op amp connected in a negative feedback configuration that is the o/p connected to the inverting terminal tried to produce the same voltage at the inverting node as we applied to ... the inverting node at the ground potential and whatever the difference between these two nodes are amplified.

Description : Why the input impedance of OP-Amp is so high?

Last Answer : Ans-In OPAMP we have 4 stages 1st stage i.e the input stage is a dual i/p balanced o/p opamp whose i/p resistance is v high. and if we use FET in case of BJT for 1st stage diffamp then i/p resistance will be v high in M ohms.

Description : Why the shape of OP-AMP is triangular not other shape?

Last Answer : Ans-The Triangular shape symbolizes that it works for continous signals and hence forth it is an analog device. ex: Opamp If it is square then it is digital device. ex: Multiplexer If the shape is both triangular and square then it is mixed signal device. ex: ADC DAC

Description : Why the input resistance of an ideal OPAMP is infinite and output resistance is zero? secondly, how can we measure these resistances(input and output) in case of an ideal OPAMPand Real OP-AMP in the following conditions when 1- load is not connected. 2- load is connected.

Last Answer : Ans- Ideal OP-AMP is a power ful concept. If one goes through the history of amplifying devices it becomes clear that less it loads the previous stage better the output signal. ie ... . Can refer application notes by device manufacturer available in internet for more precise and practical solutions.

Description : Why are the 2 input terminals of an op-amp are called as inverting & non-inverting terminals?

Last Answer : Ans-Because if we give input to one input means that will produce the same phase output where as the other(Inverting) pin produce 180 degree phase shifted output.

Description : what is meant by virtual ground in the op amp ?

Last Answer : Ans-Ideally the output of op-amp should be zero. So for this to happen the 2 inputs must be same. Hence one of the input is considered to be low or at ground potential. But this input is not actually ground hence it is called as virtual ground.

Description : Basic Op Amp Circuits

Last Answer : In this chapter we will be examining some common uses of op amps. Where Chapter Three focused on the theory of negative feedback in a more abstract way, this chapter zeroes in on the practical ... on using op amps with a single polarity power supply and how to increase the available output current.

Description : Draw pin diagram of Op-Amp IC-741.

Last Answer : Pin diagram of Op-Amp IC-741 :

Description : Describe the concept of virtual ground with reference to op-Amp.

Last Answer : Virtual ground concept:-In circuit point A is virtual ground. Figure shows inverting amplifier using op-amp. In this circuit non-inverting terminal is connected to the actual ground. Due to ... zero potential without actually grounding is known as virtual ground concept. Circuit diagram: 

Description : Block Diagram of op-Amp

Last Answer : Block Diagram: The OP-AMP is basically a different amplifier i.e. it will amplify the voltage which is differentially present between its input terminals.  1.Input stage: The ... normally a complementary output stage. It increases the OPAMP. It also provides a low output resistance. 

Description : Define the following terms related to Op-Amp: i) CMRR ii) SVRR

Last Answer : Definition:- i) SVRR: It is defined as the ratio of change of input offset voltage to the change in one supply voltage while keeping other supply voltage constant. Ideally,SVRR=0  ii)CMMR:-The ... gain should exceed common-mode gain, this will be a positive number, and the higher the better.

Description : State any two characteristics of an ideal Op-amp.

Last Answer : Characteristics of Op-amp: i) Input offset voltage ii) Input offset current iii) Input bias current iv) Differential input resistance v) Input capacitance vi) CMRR-common mode rejection ration vii) ... voltage rejection ratio(SVRR) viii) Output resistance ix) Voltage gain x) Bandwidth xi) Slew rate

Description : An Op-amp as a voltage follower has a voltage gain of

Last Answer : An Op-amp as a voltage follower has a voltage gain of Unity

Description : The input impedance of an op-amp is • High • Low • Medium • None of the above

Last Answer : The input impedance of an op-amp is High

Description : An OP-AMP can be classified as  1.Linear amplifier 2.Low - Rin amplifier 3.Positive - feedback amplifier 4.RC - coupled amplifier 

Last Answer : An OP-AMP can be classified as Low - Rin amplifier

Description : In op-amp operation, Common Mode Rejection Ratio (CMRR)

Last Answer : In op-amp operation, Common Mode Rejection Ratio (CMRR) is desired to be high

Description : In a 741 Op-Amp, there is 20 dB/decade fall-off starting at a relatively low frequency. This is due to the (A) applied load (B) internal compensation (C) impedance of the source (D) power dissipation in the chip

Last Answer : In a 741 Op-Amp, there is 20 dB/decade fall-off starting at a relatively low frequency. This is due to the internal compensation

Description : An OP amp has an open loop gain of 1,00,000. If the feedback fraction is 0.02, the approximate closed loop gain is (a) 1 (b) 1,00,000 (c) 50 (d) 0.02

Last Answer : The closed loop gain Ag = G/(1+G*f) Where G is the open loop gain and f is the feedback fraction  So Ag = 49.975

Description : An OP amp has a slew rate of 1V/µs. At a signal frequency of 0.1 MHz, the maximum undistorted sine wave amplitude is (a) 8V (b) 4.82 V (c) 2.02 V (d) 1.592 V

Last Answer : Slew rate = 2πfv where v is the amplitude V=(1/2π*0.1) = 1.592V

Description : The closed loop gain of an OPAMP is dependent upon, whether the OP AMP is used : -  a) in inverting mode b) in non -inverting mode c) is independent of the fact whether the ... inverting terminal d) is depending upon the fact whether the input is connected to inverting or non -inverting terminal

Last Answer : The closed loop gain of an OPAMP is dependent upon, whether the OP AMP is used : - is depending upon the fact whether the input is connected to inverting or non -inverting terminal

Description : The input voltage to an OP AMP is a large voltage step. The output is an exponential waveform that changes to 0.25 V in 0.1µs (microsecond). The slew rate of the OP AMP is : -  a) 5V/µs b) 2.5 V/ µs c) 3V/µs d) 4.5V/ µs

Last Answer : The input voltage to an OP AMP is a large voltage step. The output is an exponential waveform that changes to 0.25 V in 0.1µs (microsecond). The slew rate of the OP AMP is : - 2.5 V/ µs