1. In the beginning of class, we write down five circuit elements we covered so far. We write down resistor, voltage supply, current supply, diode, transistor.
2. Today, we talk about the new element: operational amplifier (op amp)
We do a pre-lab to see that the relationship between V in and V out. We find that theoretically the relationship would be Vout= -2 Vin (in this problem).
In order to do this experiment, we build a circuit like the graph in the pre-lab.
We use a 1.8k ohm and 3.6k ohm resistor.
We measure their real values to be 1.76k Ohm and 3.6K Ohm.
In order to find the saturation region of the op-amp, we supply voltage from -3V to 4V.
From the graph, we can see that the saturation region are from -2 V to 2 V.
Discussion:
We find that that the output voltage start to not changing (saturation area) when the input voltage is higher than 2V or lower than-2V. Ideally the output voltage of the op-amp should be 5V (or -5V); since the op amp is cheap, and the internal of op amp is very complex, there are some voltage loss. There could be some ways to improve this op amp, but it will just cost lots of money and becomes way more expansive.
Summary:
Today, we talk about operational amplifiers, and explain the internal of it. Most time, we can treat op amp as ideal op amps and let their open-loop gain and input resistance go to infinity and their output resistance go to zero. Once we treat it as ideal op amp, we have an important property that both input currents become zero and thus the input two voltage would be the same.
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