San José State UniversityCollege of Engineering/Electrical Engineering

EE174: Analog Peripheral for Embedded Systems

Fall 2018Lab #1: Op-Amp

Purpose:To understand and become familiar with the basic principle of the operational amplifier (Op-Amp) and be able to build various types of op-amp application circuits.

References:• Class Notes• Op-Amp 741 specifications

Equipment:• Breadboard, Op-Amp LM741 (3x), resistors: 100Ω (1x), 2kΩ (1x), 5kΩ (3x), 10kΩ (4x),

100kΩ (1x), 1MΩ (1x) and capacitor: 0.03uF, 1uF.• Power supplies and functional generator

Pre Lab Exercises:• Read the data sheet for the LM741 Op-Amp and fill in the following parameters.

Supply Voltage: Bandwidth:

Input Offset Current: Input Offset Voltage:

Slew Rate: Input Voltage:

Supply Current: Power Consumption:

• Calculate overall gain A = VO/V1 of the circuit below. What is the input voltage V1 when the output voltage is VO = – 9.98V?

Lab Exercises:1. Assemble a non-inverting amplifier with a gain of 1001 in Figure #1 below.

a) Input offset voltage and noise measurements: Short the non-inverting input to GND. The amplifier now amplifies its own noise, Vnoise, and input offset voltage, Vo. Measure and record the Vo using your DMM, and with the help of an oscilloscope, estimate and record the Vnoise.

b) Input current measurements: To measure the input current, measure ΔVO) where ΔVO is the difference in the output voltage VO with Rin shorted or not shorted to GND.The current into the input causes a voltage drop across R in, which is amplified in the same way as VO. Measure and record the input current, Ibias is given by Ibias = ΔVout/(1001 x Rin).

Figure #1:

2. Build and test the basic forms of amplifiers as shown in Figure #2 below. a) Select R1 = 5kΩ, R2=5 kΩ, R3=5 kΩ and R4=10 kΩ to obtain a closed loop gain of 2

for the non-inverting circuit U2 and the inverting circuit U3. Measured the R1, R2, R3 and R4 to obtain actual values and calculate actual gain for U2 and U3 circuits.

b) Apply +15V and –15V to V+ (pin 6) and V– (pin 4) respectively.

Figure #2:

c) Apply 1 kHz, 5V square wave (or sinewave) to obtain output voltage V1, V2 and V3. Compare the theoretical voltage gain from the above equation with the experimental value obtained by dividing output voltage by input voltages observed. Record the error in %.

d) Measure and record the inputs v+ and v_ of each op-amps (U1, U2, U3).

e) Slew rate: Use result of unity gain circuit shown above when apply 1 kHz and 5V square wave, measure the slew rate and compare with the LM741 specification.

f) DC Transfer Characteristics - Study the saturation limits for an OP-Amp by applying an input of 1V p-p sinewave and record the input and output. Observe the output and explain the results. Record voltage values at non-inverting input v+ and inverting input v-.

g) Frequency Response:Select R3=2 kΩ and R4=100 kΩ to obtain a closed loop gain of 50 for the inverting op-amp circuit U3.Apply 10 Hz, 200 mV p-p and obtain the output voltage & measured gain. Measure the gain for different frequencies between 10 Hz and 10 MHz.

Frequency Input Voltage Output Voltage Measured Gain

10 Hz

20 Hz

50 Hz

100 Hz

1 kHz

10 kHz

100 kHz

500 kHz

1 MHz

10 MHz

h) Plot the measured gain versus frequency and compare with the specification of the LM741.

i) Integrator: Build the integrator amplifier with R1 = R2 = R3 = 10 kΩ, C = 0.03μF (gain of 1) below.

Apply an input of 1V DC. Observe and record the output. Explain the result. Apply an input of 2 volt p-p at 1 kHz square wave. Observe and record the

input and output of the integrator. Use AC gain formula to verify the gain. Change C = 1μF, record the output. Observe and record the output. Explain

the result (Hint: use AC gain formula).

Figure #3:

Summary Report and Demonstration:Write a detail summary, turn in the complete report (hard copy and email soft copy) and demonstrate your results.