(5.1):

Properties of an ideal operational amplifier:

• Infinite input impedance.

• Zero output impedance.

• Zero common-mode gain, or, infinite common-mode rejection.

• Infinite open-loop gain.

• Infinite bandwidth.

(5.2):

Operational amplifiers are normally used with feedback around the amplifier element itself.

Open loop gain: This form of gain is measured when no feedback is applied to the operational amplifier.

In other words it is running in an open loop format. Gain figures for the op amp in this configuration are normally very high, typically between 10,000 and 1,00,000.This is the gain of the operational amplifier on its own.

Closed loop gain: This form of gain is measured when the feedback loop is operation, i.e. a closed loop.

By applying negative feedback, the overall gain of the circuit is much reduced, and can be accurately tailored to the required level or to produce the required output format as in the case of filters, integrators, etc.

The gain is measured with the loop closed and provided there is a sufficient difference between the open loop and closed loop gain, the circuit will operate according to the feedback placed around it.

(5.3)

The capacitance of a integrator amplifier is $\"\"$ .

The input resistance is $\"\"$ .

The input volatage is $\"\"$ .

The rate of change of output voltage is $\"\"$ .

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$\"\"$ .

Step 4:

SCR is a four-layer device.

SCR consist of three terminals anode cathode and the gate.

When the anode is made positive with respect to the cathode, junctions J₁ and J₃ are forward biased and junction J₂ is reverse-biased.

Leakage current will flow through the device. The SCR is then said to be in the forward blocking state or in the forward mode or off state.

The triac has on and off state characteristics similar to SCR.

Characteristic is applicable to both positive and negative voltages.

Triac consists of two SCR connected in parallel but opposite in directions.

Differences between SCR and TRAIC:

SCR: 1.SCR is a unidirectional device. 2.The gate current can be only positive. 3.SCR can operate in only one quadrent of v-i characteristics. 4.UJT is used for triggering SCR. TRIAC: 1.TRIAC is a bi-directional device. 2.Gate current can be positive or negative. 3.It can operate in two quadrants of v-i characteristics. 4.Diac is used for triggering triac .

(5.4)

Comparator amplifier:

Comparator is a device which compares two voltages or currents, and switches its output to indicate which is larger.

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Comparator is a device which compares two voltages or currents, and switches its output to indicate which is larger.

It has two analog input terminals $\"\"$ and $\"\"$ and one binary digital output $\"\"$ .

The output is ideally $\"\"$ .

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In electronics, a comparator is a device that compares two voltages or currents and outputs a digital signal indicating which is larger. It has two analog input terminals $\"V_+\\,\"$ $\"\"$ and $\"V_-\\,\"$ $\"\"$ and one binary digital output $\"V_o\\,\"$ . The output is ideally $\"\"$ .

Light activated SCR (LASCR) or a Photo SCR is just an ordinary SCR except that it can also be light triggered. Most LASCRs also have a gate terminal for being triggered by an electrical pulse just as a conventional SCR.

A silicon controlled rectifier is a semiconductor device that acts as a true electronic switch. It can change alternating current into direct current and at the same time can control the amount of power fed to the load. Thus SCR combines the features of a rectifier and a transistor.

The light-activated SCR(LASCR) is the light sensitive equivalent of the normalSCR.

As the name suggests, its state is con-trolled by the light falling on depletion layers.

In a normal SCR, gate current turns on the device. In the LASCR, instead of having the external gate current applied, light shinning on the device turns it ON. Just as a normal SCR, the LASCRwill continue to conduct even if the light source is removed. The LASCRs find many applications including optical light controls, relays, phase control, motor control and a large number of computer applications. The maximum current (r.m.s.) and power (gate) ratings for LASCRs commercially available today are about 3A and 0.1W. It may be noted that LASCR is most sensitive to light when the gate terminal is open. Its sensitivity can be reduced and controlled by the insertion of a gate resistor.

Circuit of an LASCR by transistors

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(6.4)

Construction of TRAIC:

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Triac is a semiconductor device of three terminals that is used to control the average current flow to a load, with the particularitity of which it leads in both senses and it can be blocked by investment of the tension or when falling the current below the value of maintenance.

1. Triacs are bidirectional devices.

2. Triac is designed to conduct load current in either direction.

1.Ι + Mode = MT2 current positive (+ve), Gate current positive +ve)

2.Ι – Mode = MT2 current positive (+ve), Gate current negative(-ve)

3.ΙΙΙ + Mode = MT2 current negative (-ve), Gate current positive(+ve)

4.ΙΙΙ – Mode = MT2 current negative (-ve), Gate current negative(-ve).

Definition of Quadrac:

Quadracs are a special type of thyristor which combines a diac and a traic in a single package.The diac is the triggering device for the triac.

Therefore, the statement is true.

The gain of an operational amplifier or op-amp circuit depends upon a variety of factors including the circuit configuration as well as the components around the operational amplifier chip itself. This page gives a summary or overview of the gain of the different operational amplifier circuits available.

Most op amp chips have very high gain levels, typically of the order of 10 000 to 100 000 at very low frequencies.

Although this gain is not directly used, as it would mean that even very small input signals would send the chip into limiting, by using negative feedback high performance circuits can be generated.

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(5.2)

Internal gain of the operational amplifier is the open loop gain of the amplifier.

This gain can be controlled or changed by providing feedback in the amplifier.

Feedback

Circuit characteristics such as the systems gain and response can be precisely controlled.
Circuit characteristics can be made independent of operating conditions such as supply voltages or temperature variations.
Signal distortion due to the non-linear nature of the components used can be greatly reduced.
The Frequency Response, Gain and Bandwidth of a circuit or system can be easily controlled to within tight limits.

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