![]() ![]() ![]() Analog circuits usually need some fine tuning due to tolerances, etc. I used actual pots in the circuit so I could fine tune things as needed. Self-biasing manual is a technique used in electronics to bias a circuit automatically, without the need for external components. ![]() Note the wiper positions on the pots are approximate. 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. The 5V DC source goes into a potentiometer voltage divider to select the DC offset to be summed with the sine wave. This goes into a potentiometer voltage divider to be scaled down (to scale up you need to adjust the OpAmp feedback network). The sine wave voltage source represents the output of the uC, ranging from 0.0-5.0V. This circuit uses a non-inverting summing amplifier to do just that. For it to act as an amplifier, the base is biased with a current from the supply to result in the transistor being in the active mode. So I wanted to scale the values in an analog circuit. 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. The microcontroller of course puts out 0-5V (with PWM, but I smooth that with an RC). 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. I wanted the transistor to always be in the linear region, never shut off, even when the output from the uC was 0V. I designed this to use with a real circuit where I was using a microcontroller to control the base of a transistor. This is a non-inverting summing amplifier with input scaling, and offset. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |