Lab 4 - EE 420L 

Authored by Iain Drews, drewsi2@unlv.nevada.edu

Today's date: 2/26/2015 

Lab description:

In this lab we used Op-Amps as ampliers and learned about the gain bandwidth product (GBP)

For the following questions and experiments assume VCC+ = +5V and VCC- = 0V.

• Estimate, using the datasheet, the bandwidths for non-inverting op-amp topologies having gains of 1, 5, and 10.
• The Listed GBP on the datasheet is 1.3Meg Hz

• so for a gain of 1: the Badwidth should be up until 1.3Meg Hz
• for a gain of 5: we take the GPB/5 so we get 260K Hz
• for a gain of 10: GPB/10=130k Hz
  

• Experimentally verify these estimates assuming a common-mode voltage of 2.5 V.
• Your report should provide schematics of the topologies you are using for experimental verification along with scope pictures/results.

• Associated comments should include reasons for any differences between your estimates and experimental results.
• Gain of 1
• First Tests

Gain of 1 At 100kHz
Gain of 1 At 500kHz
Gain of 1 At 1.3MegHz

• Note how the Bandwidth product is much less then GBP
• this is because the Op amp we are using will only hit its optimal values for the GBP at and around its maximum VCC+ of 30V 
• For comparison lets look at what those reading would be like with a VCC+ of 30V

Gain of 1 At 100kHz VCC+ 30V
Gain of 1 At 500kHz VCC+ 30V
Gain of 1 At 1.3MegHz VCC+ 30V

• For the rest of the measurements we will be finding the 3DB Frequency or the Frequency where is gain is 3DB less then its optimal gain this is the equivalent of Vin*Gain/Sqrt(2) or Vin*Gain*.707

• Gain of 5 At 140kHz	Input: 216mv PK-PK 216*5*.707= 763.6 Output: 792mV PK-PK
  Gain of 10 At 65KHz	Input: 224mv PK-PK 216*10*.707= 1527 Output: 1.60V PK-PK

• Repeat these steps using the inverting op-amp topology having gains of -1, -5, and -10. 

• Gain of 1 At 810kHz	Input: 208mv PK-PK 208*1*.707= 147 Output: 144mV PK-PK
  Gain of 5 At 120kHz	Input: 208mv PK-PK 208*5*.707= 735 Output: 744mV PK-PK
  Gain of 10 At 55KHz	Input: 220mv PK-PK 220*10*.707= 1555 Output: 1.48V PK-PK

  
  

• Design two circuits for measuring the slew-rate of the LM324. One circuit should use a pulse input while the other should use a sinewave input.
• Provide comments to support your design decisions.
• Comment on any differences between your measurements and the datasheet’s specifications.

• The key to finding slew rate is to be able to bassically zoom in on the points where the sinusoidal wave would be verticle. one of the easiest ways to do this is to simply speed up a -10 multiplier until the output becomes a sawtooth waveform then measure the rise and fall time of the sawtooth 
• the slew rate will can be derived from the equation Slew Rate = (PK-PK Voltage) / ((Rise,Fall time)

PK-PK Voltage: 1V Rise,Fall Time: 2.164us 1V/2.164us= 0.46 V/us
PK-PK Voltage: 1V Rise,Fall Time: 2.220us 1V/2.220us= 0.45 V/us