Engineering 44 jwcook

In this lab we used a dual input/output op-amp to design a circuit that would sum and invert two input voltages and then perform a second sum and inversion to yield a final result. As seen below, the first op-amp would yield the inverse of the sum of half of V1 and half of V2. With inputs of 1 and 2 volts this would yield -1.5V. The second op amp uses a voltage divider for the non-inverting input to ensure the circuit is below saturation voltage. The output of the first op-amp is connected to the inverting input of the second op-amp to invert the voltage from the first stage and yield a positive output voltage from the second op-amp. As seen above, the output voltage was different from our anticipated voltage but the sign of the voltage was as expected. The output of the first stage was much closer to the anticipated value from the calculations. When we plugged in the output from the first stage into the calculation with the actual resistances of the resistors used ...

In this lab, we designed an inverting op-amp and tested the output voltages and various input voltages to test the operation. Below is our design for an inverting op-amp with a gain of 2. Vin (Volts) Vout (Volts) -3 3.58 -2.5 3.58 -2 3.58 -1.5 3.16 -1 2.11 -0.5 1.06 0 0 0.5 -1.02 1 -2.07 1.5 -3.12 2 -4.17 2.5 -4.25 3 -4.23 3.5 -4.24 4 -4.24 The table shows the output voltages measured at various input voltages. As seen above, the saturation voltages were 3.58V and -4.24V. The circuit response was linear from -1.5 to 2 volts, essentially between saturation voltages. The average gain for the op-amp was -1.743. The op-amp inverted the input voltage and our gain was nearly 2 for our circuit. The most interesting observation was that the positive and negative saturation voltages were not equal in magnitude.

Lab 6: From Dusk Till Dawn In this lab we created a simple circuit using a breadboard, resistors, a transistor, a photocell, and an LED. A power supply is connected to the circuit. When the light levels are low, the photocell has a very high resistance and at high light levels it has a low resistance. The BJT acts as a switch in this circuit. When it is dark, the photocell has a high resistance which causes current to flow through the LED causing it to light up. When it is bright in the room, the photocell has a low resistance and the BJT sends no current through the LED.  For the pre-lab we calculated the voltage, V B across the photocell with a resistance of 5k ohm and 20k ohm, respectively.  We operated the circuit and measured voltage across the photocell. Measured voltage with the photocell covered was 3.2 V versus 3.33 V predicted. Measured voltage with the photocell uncovered was 1.1 V versus 1.7 V predicted.