Amplifier
Objective
To make sure that all the amplifiers work individually and output a gain of 5.
Proof of Concept
Input a DC voltage and measure the DC output voltage of each amplifier for various voltage values, ranging from 0-15 volts. The amplifier has a control voltage of 15V. Calculate the gain of the amplifier by dividing the output voltage by the input voltage. The output voltage will be measured with a multimeter.
Known Parameters: vout = vin 1 + R2/R1
vin = 5 V, v- = GND, v+ = 15 V,
R1 = 8 k, R2 = 32 k
Pass criteria: vout = +/- 0.02 V
Fail criteria: vout = +/- 0.03 V or more
Methods
Find ratio of R2R1such that vout = 3(vin), since maximum vin provided by the DAC is 5 V and maximum desired vout is 15 V for supplying the JSPHS-1000+ Phase Shifter’s control voltage. Therefore, we would need a voltage gain of Av = vout/vin = 3 V/V. However, this voltage gain is the absolute minimum we would need, so we have actually chosen to increase our desired Av to 5 V/V to compensate for any potential loss. From these assumptions and calculations, we concluded that any value may be selected for R1 and R2, as long as the ratio of R2R1 is equal to 4. We did note the values of R1 and R2 will also vary the value of the current leading into the Bias pins of our JSPHS-1000+ phase shifters. Since the DC input resistance at the Control port, or Bias pins, of these phase shifters is typically 18200 ohms2 , this means the minimum current required would be equal to (15 V / 18200 ohms), or roughly 0.8 mA. The typical output current provided by the LM7358 operational amplifiers ranges from 10 to 20 mA3 , which means any amplifier configuration will satisfy the necessary input Bias current of 0.8 mA for the phase shifters. Knowing this, and given that we are using ¼ W resistors, we have chosen R1= 8 kohms and R2 = 32 kohms. In order to validate our results even further, we conducted another test with our final amplifier configuration and recorded the input/output voltage values and gain.
Results
Amplifier 1
![Output Voltage (V) vs. Control Input Vo](https://static.wixstatic.com/media/d427e6_59b86ebc3b4a4cbe8294e1f40ff66e31~mv2.png/v1/fill/w_720,h_445,al_c,lg_1,q_85,enc_auto/Output%20Voltage%20(V)%20%20vs_%20Control%20Input%20Vo.png)
Resistor 1 (Ohms): 8.210
Resistor 2 (Ohms): 32.870
R2/R1 = 4.004
Our ideal resistor ratio is 4 and our ideal gain is 5 V/V for each control input voltage. We picked resistors values that are as close to our ideal resistors to make sure that our resistor ratio is 4. As you can see for each of our op - amp circuits our resistors ratios are very close to 4. As we increase the input voltage the output voltage is 5 times as large, this is how we make sure that the gain is 5 V/V because gain is output divided by the input voltage. As you can see in each of the amplifier graphs, for each of the outputs is 5 times as large. Around 2.8 V for each of the amplifiers the output voltage becomes saturated. This matches the results of the datasheet for the LM358 Amplifier.
Amplifier 1 Results
Amplifier 2
![Output Voltage (V) vs. Control Input Vo](https://static.wixstatic.com/media/d427e6_67ab3912f6d84c08abaa6f54d44c422a~mv2.png/v1/fill/w_720,h_445,al_c,lg_1,q_85,enc_auto/Output%20Voltage%20(V)%20%20vs_%20Control%20Input%20Vo.png)
Resistor 1 (Ohms): 8.20
Resistor 2 (Ohms): 32.87
R2/R1 = 4.009
Amplifier 2 Results
Amplifier 3
![Output Voltage (V) vs. Control Input Vo](https://static.wixstatic.com/media/d427e6_bd0ec883aec5471f8e1d8fe2d70b6c7d~mv2.png/v1/fill/w_720,h_445,al_c,lg_1,q_85,enc_auto/Output%20Voltage%20(V)%20%20vs_%20Control%20Input%20Vo.png)
Resistor 1 (Ohms): 8.19
Resistor 2 (Ohms): 32.84
R2/R1 = 4.010
Amplifier 3 Results
Amplifier 4
![Output Voltage (V) vs. Control Input Vo](https://static.wixstatic.com/media/d427e6_e336e3b0b41a4945a6527a2fd02bc0f7~mv2.png/v1/fill/w_720,h_445,al_c,lg_1,q_85,enc_auto/Output%20Voltage%20(V)%20%20vs_%20Control%20Input%20Vo.png)
Resistor 1 (Ohms): 8.20
Resistor 2 (Ohms): 32.79
R2/R1 = 3.999
Amplifier 4 Results
Images
Amplifier Test
![IMG_0163.jpg](https://static.wixstatic.com/media/d427e6_52e0180e5b4d418f999c77090ed9dc4f~mv2.jpg/v1/crop/x_0,y_531,w_3024,h_2553/fill/w_854,h_721,al_c,q_85,usm_0.66_1.00_0.01,enc_auto/IMG_0163.jpg)
Amplifier Test Set Up
Amplifier Boards
![IMG_0162_edited.jpg](https://static.wixstatic.com/media/d427e6_b6976921d7a74eada1b4ab5b4c738955~mv2.jpg/v1/crop/x_433,y_345,w_1764,h_1167/fill/w_845,h_559,al_c,q_85,usm_0.66_1.00_0.01,enc_auto/IMG_0162_edited.jpg)
Amplifier Boards