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This is a non-inverting summing amplifier with input scaling, and offset.
I designed this to use with a real circuit where I was using a microcontroller to control the base of a transistor. I wanted the transistor to always be in the linear region, never shut off, even when the output from the uC was 0V.
In my case, with the bias resistor I chose, the transistor needed to be in the range of about 0.6V to 5V in order to stay linear and produce the desired output. The microcontroller of course puts out 0-5V (with PWM, but I smooth that with an RC). So I needed to scale 0.0-5.0V to 0.6-5.0V. If I simply remapped the values in the uC by using a higher value as my zero point I would lose resolution in the already narrow 8bit range. So I wanted to scale the values in an analog circuit.
This circuit uses a non-inverting summing amplifier to do just that.
The sine wave voltage source represents the output of the uC, ranging from 0.0-5.0V. This goes into a potentiometer voltage divider to be scaled down (to scale up you need to adjust the OpAmp feedback network). Thus we can scale 0.0-5.0V down to 0.0-4.4V.
The 5V DC source goes into a potentiometer voltage divider to select the DC offset to be summed with the sine wave. So here we can add our 0.6V offset to the 0.0-0.4V range produced above and get our desired 0.6-5.0V range.
Note the wiper positions on the pots are approximate. I used actual pots in the circuit so I could fine tune things as needed. Analog circuits usually need some fine tuning due to tolerances, etc.
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