I ONLY NEED HELP FROM PL6 to PL10 Figure 1 shows a diagram of an operational amp

Question

I ONLY NEED HELP FROM PL6 to PL10

Figure 1 shows a diagram of an operational amplifier with two inverting inputs and two non-inverting inputs.

V- is the voltage on the inverting input of the amplifier while V+ is the voltage on the non-inverting input.

A 1V test signal at 1 kHz and the other inputs are grounded.

The output voltage is VO. We will use a 741 op amp. (Hey...they were cheap!)

Assumptions: 1. The input impedances of the amplifier are infinite. No current flows into or out of the V+ or Vterminal.

2. The output impedace of the amplifier is zero.

3. The gain of the amplifier is infinite, Av = ?.

4. The performance of the amplifier is independent of frequency.

5. The system is linear.

6. The amplifier output VO is always between - VCC and + VCC (the power supply rails). We will use VCC = 12 Volts for this experiment, so |VO| <= 12

7. The output is related to the inputs by the equation

VO = Av*(V+ - V- )

When assumption 3 is used in conjunction with assumption 7 we can conclude that

| (V+ - V- ) | = __________

This is often called "the principle of the virtual short". (Refer to question PL1)

You will be using a 741 operational amplifier in this laboratory. Data from National Semiconductor on this device is inluded in this lab.

Prelab Phase

The output voltage will be a linear combination of the input voltages

VO( VII1, VII2 ,VINI1,VINI2,RII1,RII2,RNII1,RNII2,RF) := ?AVII1?VII1 ? AVII2 VII2 ? + AVNII1 VNII1 ? + AVNII2 VNII2 ?

PL1. Why do they call it a "virtual short"?

PL2. Find the gain coefficients (AV*) in terms of the circuit parameters (R*).

PL3. If the circuit values are RII1 30000 = RII2 60000 = RNII1 20000 = RNII2 30000 = RF 120000 = ? write out the equation for VO in numerical form. (The inputs are still literal, however.) VO = _________________________________________________________________________

PL4. Write a simulation for this system using a 741 op amp...don't forget to connect the +VCC and - VCC supplies and ground.

PL5. Generate a test plan using the simulation to test each channel gain individually and verify your analysis. Use a test sinusoidan voltage of 1 V (peak) if this is feasible. Make a table summarizing the calculated gain of each channel and the gain you obtained using simulation. Leave room for the future ... the experimental results. Each of you should document your analyses and show an example of a simulation test.

PL6. What output voltage do you expect when the 1 V test signal is applied to only the two inverting inputs?

PL7. What output voltage do you expect when the 1 V test signal is applied to only the two non-inverting channels?

PL8. What output voltage do you expect if all the inputs are a 1 V (peak) sine wave?

PL9. Run your simulation and corroborate your analyses. Be sure and tell the grader WHAT you're doing, WHAT the results were and whether there is agreement between them.

PL10. Why might it not always be feasible for systems having large gains?

Explanation / Answer

PL6->Due to the 1V test signal given to the inverting input the output is 180 degrees out of phase with the input signal. PL7=>due to the 1v test given to the non inverting input the output is 0 degress with the input signal. PL8=>The output voltage of an OPAMP is given by V0=AD(V1-V2)WHERE AD is gain of the amplifier and v1 is inverting input voltage and v2 is non inverting input amplifer since v1 and v2 are same the output voltage is zero. PL10=>IF we use the larger gains in different amplifications then the feasiblity depends on the gains what we are using...

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