Op Amp Lab

Problem 1: Slew Rate

Design an experiment to measure the slew rate of one of the channels of a LM324 or LM348 Op-Amp and represent the slew rate in the units of V/μs.  Compare the value you measure to the spec. sheet.  Hint: Use a square wave.  The slew rate can be determined from Figure 7 of the spec. sheet.

Circuit Setup

Problem-1

Input: 10v square @ 50%, 1KHz

Slew Rate = (==)

Problem-1-Slew-Rate

Problem 2

Design an experiment to measure/calculate the unity gain bandwidth AND the gain-bandwidth product of one of the channels of a LM324 or LM348 Op-Amp.  Using the finite gain equation, set A0 = 1 and calculate the output voltage with the resistor ratio and input voltage amplitude you used.  Increase the frequency until the output is at the value you calculated.  Compare the value you measure to the spec. sheet.  The unity gain bandwidth can be determined from Figure 5 of the datasheet.

Circuit Setup

Problem-2

Ideal:


$$\frac{V_0}{V_i}=1+\frac{R_2}{R_1}$$


Vin = 200mv


Vout = 183mv@825KHz

Problem-2-scope

Problem 3

Find a potentiometer in the lab and design an Op-Amp circuit using the LM324 or LM348 that will have an adjustable gain from 15dB to 35dB.  (± 1 dB tolerances).  Make the input voltage a 200 mV peak to peak sine wave input at 500 Hz.  When the potentiometer is turned all the way counter clockwise the gain should be 15dB and when it is turned all the way clockwise the gain should be 35dB.  The TA must verify functionality by adjusting the potentiometer to max and min settings.  Either a non-inverting or inverting amplifier configuration can be used.  YOU MUST use dual supplies and have an output that is symmetrical about the y axis.

Circuit Setup

problem-3-circuit

Input: (200mv_{pk} at 500Hz)

Clockwise: 6v


$$gain = 20log(\frac{6v}{200mv})=29.54dB$$

Problem-3-CW

Counter-clockwise: 560mv


$$gain=20log(\frac{560mv}{200mv}=8.9dB$$

Problem-3-CCW

Problem 4

Design an Op Amp filter that has a gain of 12 V/V +/- 0.5 V/V between 150 Hz and 10 kHz and less than 1 V/V gain for frequencies less than 5 Hz and greater than 150 kHz.  To prove the design meets the specifications do at least 5 screen shots of Vi and Vo at 5 Hz, 150 Hz, 2 kHz, 10 KHz, and 150 KHz.  Using these and additional data points sketch the bode magnitude plot (dB vs Hz).

Circuit Setup

Highpass Stage

Cutoff Frequency: 150Hz

Highpass

Lowpass Stage

Cutoff Frequency: 10KHz

Lowpass

Gain Stage

gain-stage

5Hz

Problem-4-5Hz

150Hz

Problem-4-150Hz

2KHz

Problem-4-2KHz

10KHz

Problem-4-10KHz

150KHz

Problem-4-150KHz

 Problem 5

Using the square wave from the function generator as the input, build an integrator circuit using a LM324 or LM348 Op-Amp that will convert the waveform to a triangle wave.  Adjust the duty cycle of the square wave and comment on how it affects the triangle wave and show a screen shot.

Circuit Setup

Problem-5

Input: (200mv_{pk-pk} @ 70Hz)

Duty Cycle: 0%

Problem-5-

Duty Cycle: 50%

Problem-5-50

Duty Cycle: 100%

Problem-5-100

Conclusion

The integrator circuit, outputs the integration of the input signal. -Integrating a square function produces a triangle function.

Problem 6

Design a 2 kHz sine wave oscillator circuit using the LM324 or LM348 Op-Amp.  There are many ways to do this.

Circuit Setup

Wein-Bridge Oscillator

Problem-6

Problem 7

Input a 500 Hz 200 mV peak to peak sine wave to a LM 386 IC that has a gain adjustment from 30 V/V to 40 V/V.  The potentiometer should produce a gain of 30 V/V when turned all the way one direction and 40 V/V when turned all the way the other direction.  Plot the input and output on the scope for both gain settings.  Next, send the LM386 output to a speaker.  With the speaker attached at the 40 V/V gain setting plot the output on the scope and explain what you see.

Circuit Setup

Problem-7

Gain measured: 30v/v -45v/v

Problem 8

Using the provided thermistor, build a circuit using the LM386 that turns on a fan whenever the temperature gets too hot (simulate this by holding your finger over the thermistor).

Circuit Setup

Problem-8

 Individual Design

Design an instrumentation amplifier using the LM324 or LM348 Op-Amp with a gain of 10 V/V (See MultiSim file on D2L). To test the differential input, do the following:

Using the function generator add a DC offset to your sine wave input on the non-inverting terminal.  Add a 9V battery (or an extra DC supply) with a voltage divider on the other terminal that has nearly the same value as the DC offset that was added to the sine wave.  If done correctly the DC will be subtracted and the result will be no DC offset.  Make sure you have the scope in DC coupling mode.

Circuit Setup

indiv

photo