UNIVERSITY OF THE EAST
COLLEGE OF ENGINEERING
ELECTRONICS ENGINEERING DEPARTMENT

NEC 327 - ECE2
COMPUTER-AIDED ELECTRONIC CIRCUIT DESIGN
WED / 2:30 – 5:30 / EN308

ACTIVITY #6: OP-AMP INTERGRATOR
ACTIVITY #7: SUMMING OP-AMP
RATING
RATING

3, 2

QUIAMBAO, PATRICIA MAE M.
20140169557

FERNANDO VICTOR V. DE VERA, ECE, M.TECH

MARCH 16, 2016

Activity No 6: OP-AMP Integrator 6.1 Objectives To capture and simulate a circuit where a waveform conversion is present while the output voltage is proportional to its integral voltage input of the amplifier. 6.2 Theoretical Discussion The integrator circuit is mostly used in analog computers, analog-to-digital converters and wave-shaping circuits. A common wave-shaping use is as a charge amplifier and they are usually constructed using an operational amplifier though they can use high gain discrete transistor configurations.
The integrator basically works like this: whatever current I you get flowing in R1, gets integrated across capacitor C1. The output voltage Vo is simply the voltage across C1. One great application of the integrator is generating a ramp voltage. You can do this by placing a fixed voltage at VS that forces a constant current through R1. The capacitor then integrates this current creating a ramping voltage. The action is just like a garden hose running water at a constant rate causing the level in a bucket to rise steadily. The smaller the diameter bucket (smaller capacitor), the faster the increase in water level (greater voltage). The switch is needed to discharge the capacitor (empty the bucket) at the end of a ramping cycle. 6.3 Multisim Circuits PART 1: Simple Integrator

PART 2: Integrator with Current

6.4 Procedures Part 1: Simple Integrator a) Apply a square wave at Vi at 1Vpp b) Set f = 100Hz c) Note the waveforms through an oscilloscope d) Change the frequencies. Note the changes
NOTES: Set the op-amp power supply to ±15V. Close SW1 to reset to zero.
Part 2: Integrator with Current a) Set RS = 50%, Vi open, Open SW1 and adjust R8 to keep Vo = OV b) Open SW1, set Vi = 1Vpp square wave. c) If output grows or decay, adjust R5 to have a stable amplitude at the output. d) Note the values of R8 and R5 e) Adjust the input frequency to different values and note the adjusted R5. 6.5 Simulation Results Part 1: Simple Integrator
@ 100 Hz

@ 50 Hz

@ 150 Hz

Part 2: Integrator with Current
F = 100 Hz, R8 = 50%, R5 = 55%

6.6 Observations, Conclusion, Recommendation Adjusting the frequency of the circuit changes the range of the output. The higher the frequency the lower the value is of the range. The conclusion in this experiment is that higher frequency input is more convenient because it gives a better output waveform. Minimizing errors during the simulation is present if we double check connections between the components and the nodes. 6.7 References * http://www.ecircuitcenter.com/Circuits/opint/opint.htm * https://en.wikipedia.org/wiki/Op_amp_integrator

Activity No 7: Summing OP-AMP 7.1 Objectives To capture, simulate and determine the output waveform and frequency using the oscilloscope and spectrum analyze of the amplifier. 7.2 Theoretical Discussion The summing amplifier is a handy circuit enabling you to add several signals together. What are some examples? If you're measuring temperature, you can add a negative offset to make the display read "0" at the freezing point. The summing amplifier is a versatile device for combining signals. It can either add signals directly, or scale them to fit some predetermined combination rule. 1. Summing several signals with equal gains is done in an audio mixer. 2. A summing amplifier with different resistors on the inputs gives a weighted sum. This can be used to convert a binary number to a voltage in a digital-to-analog converter. 3. A summing amplifier can be used to apply a DC offset voltage along with an AC signal voltage. This is done in a LED modulation circuit to keep the LED in its linear operating range. 7.3 Multisim Circuits

7.4 Procedures 1. Copy the circuit in your multisim 2. Set: a.V1= 1Vpeak at 100 Hz b.V2= 1Vpeak at 250 Hz c.V3= 1Vpeak at 350 Hz 3. Set Potentiometer values at 100%. Use the oscilloscope to see the resulting waveform 4. Use spectrum analyzer to see the frequency components of the output 5. Change the resistance of R1, R2, R3 by adjusting the % settings. Fill out the table. 7.5 Simulation Results

Resulting Waveform in the Oscilloscope

Frequency Waveform in the Spectrum Analyzer

%R1 | %R2 | %R3 | Vout (Rms) | Frequency Components and levels | 95% | 15% | 80% | 6.10 V | 16.477 dB | 50% | 75% | 100% | 18.7 V | -45.712 dB | 20% | 40% | 60% | 4.29 V | 7.958 dB |

7.6 Observations, Conclusion, Recommendation The waveform changes proportionally while varying the potentiometer values. Summing op-amp has output voltage that is proportional to the negative sums of the input voltages. Minimizing errors during the simulation is present if we double check connections between the components and the nodes. 7.7 References * http://www.ecircuitcenter.com/Circuits/opsum/opsum.htm * http://hyperphysics.phyastr.gsu.edu/hbase/electronic/opampvar5.html