Question

URGENT!! PLEASE HELP! be clear and answer all questions clearly!!

Lab ll: Voltage Follower ECE 210: 1. For the following circuit, Theoretically calculate the peak voltage across R3 (Vo) an ved R1-2.2k0 2.17362(Actual) R2 = 3.3kN-3.Z44KAL (Actual) R3-10kΩ 9.873M. (Actual) Vin- 1kHz Triangle wave, 2V peak, NO DC offset e) R Draw the output waveform Vo: UI R1 R2 X-Axis 0.1 msec/div 2. Remove the resistor R2 to create the following circuit Draw the output waveform Vo: U1 R1 R3 A0741 Y-Axis-0.5 v/div X-Axis= 0.1 msec/div = 3. In the above circuit (without R2), how is Vo related to Vi? Why? 4. For the circuit in question 2, measure the voltage across RI using the AC setting on the DMM. From this voltage, calculate the current the current through R1. Which of the three properties of an OpAmp does this illustrate?

Answer 1

Answers :

Answer 1: In case of the first circuit

Vpp = 2V approx.

Vp = 1 V approx

Answer 2: In the second case

Vpp= 4v approx.

Vp= 2 v approx

Answer 3: When R2 is removed, the circuit is essentially a unity-gain voltage follower, i.e.

Vo = Vi

The reason is as follows:

Vo = K(Vi-Vo) where K is the open-loop gain of 741

(recall that op-amps have very large input impedance and therefore very little current flows through R1)

Vo = K*Vi/(1+K)

As K>>1, therefore K and K+1 are almost same.

Therefore Vo = Vi

This makes the circuit a voltage-follower.

Answer 4: You would have noticed a small but non-zero voltage across R1 in this case. This means that there is, after all, a small current flowing into the non-inverting terminal of op-amp. This is input bias current. For AD741 this current is of the order of 100nA.

Hope this helps.