1. ET 1410

Part 1- Linear Op-Amp Circuits

Theory:

1. Provide the formula used to calculate the closed-loop gain of a non-inverting amplifier.
2. Provide the formula used to calculate the feedback fraction.
3. Provide the formula used to calculate the closed-loop gain of an inverting amplifier.
4. For a non-inverting amplifier (Figure 2-1), what is the voltage at V₍₎ equal to?
5. For an inverting amplifier (Figure 2-2), what is the voltage at V₍₎ equal to?

Test Procedure:

1. Transcribe the non-inverting amplifier characteristic measurements from Table 2-2 to the table below.

Rf	Ri	Vin	Acl(NI)	Vout	V(-)	Rin
Measured	Measured	Measured	Measured	Computed	Measured	Measured	Measured
9.90 k	991	500mVpp	10.9	5.45V	-12.9VPin 6	-1.11VPin 2	1.1k

Table 2-2

1. What is the voltage recorded at V₍₊₎ (step 12) after the 1M resistor is inserted into the circuit?
2. For the non-inverting amplifier in Figure 2-3, if the voltage applied at pin 3 is 1Vpp, what is the voltage drop across R_i, the current though R_i, the current though R_f, and the voltage drop across R_f?
   • V_Ri =
   • I_Ri =
   • I_Rf =
   • V_Rf =
3. Transcribe the inverting amplifier characteristic measurements from Table 2-3 to the table below.

Rf	Ri	Vin	Acl(I)	Vout	V(-)	Rin
Measured	Measured	Measured	Measured	Computed	Measured	Measured	Measured
		500mVpp			Pin 6	Pin 2

Table 2-3

1. What is the voltage recorded at V_Ri (step 21) after the 1k resistor is inserted into the circuit?
2. What values of R_f and R_i where used to create an inverting amplifier with a gain of -47 and an input resistance of 10k?

1. Transcribe the inverting amplifier performance observations from Table 2-5 to the table below.

	Required Value
Vin (Clipping)
Vout (Clipping)
Effect on Vout as frequency increases)

Table 2-5

1. Express the gain of the non-inverting amplifier (Figure 2-3) in dB.
2. Express the gain of the inverting amplifier (Figure 2-4) in dB.
3. It was correct to talk about a virtual ground for the inverting amplifier. Why isn't it correct to refer to a virtual ground for the non-inverting amplifier?
4. If R_f = R_i = 10 k, what gain would you expect for a non-inverting amplifier?
5. For an inverting amplifier?
6. For the non-inverting amplifier in Figure 2-3, if R_f = 0 and R_i is infinite, what is the gain?
7. What is this type of amplifier called?
8. What output would you expect in the inverting amplifier of Figure 2-4 if R_f were open?

Part 2- Op-Amp Frequency Response

Theory:

1. What does closed-loop refer to in an amplifier circuit?
2. What formula is used to calculate the closed width bandwidth of an amplifier?
3. What does f_T represent?

Test Procedure:

1. What is the formula to calculate the decibel gain of an amplifier?
2. What decibel gain represents the 50% power point or the 70.7% voltage amplitude point of an amplifier?
3. What do we call the frequency when the output has 50% of the power or 70.7% of the voltage amplitude?
4. Transcribe the non-inverting amplifier gain and bandwidth measurements from Table 2-6 to the table below.

	Computed	Measured	Closed-loop bandwidth
Step	Gain	Gain	Computed	Measured
1	1
3	10
14	101

Table 2-6

1. Transcribe the inverting amplifier gain and bandwidth measurements from Table 2-7 to the table below.

	Computed	Measured	Closed-loop bandwidth
Step	Gain	Gain	Computed	Measured
6	-1
7	-10
8	-100

Table 2-7

1. From your data for the non-inverting amplifier (Table 2-6), determine if the gain-bandwidth product was constant. Should it be?
2. From your data for the inverting amplifier (Table 2-7), determine if the gain-bandwidth product was constant. Should it be?
3. How would you expect the bandwidth of the amplifiers in this experiment to affect the rise time of a square wave input?
4. What factor, other than bandwidth, can also affect the rise time of a square wave?
5. Is it possible to increase the bandwidth of a high-gain amplifier by substituting two lower gain amplifiers? Explain.