PWM@ Analog to Digital@ Digital to Analog@
Lots of people have asked for it so here it is, a little analog output circuit for microcontrollers that covers the common voltage and current ranges used in instrumentation.
The input can be, for example, 0-5V analog from a DAC, or 0-5V PWM signal. The 100k resistor and 1uF capacitor filter the PWM signal to make it smooth DC. With J3 ON the input becomes 1-5V to produce the offset zero ranges.
The first Op Amp is the output driver, and its feedback path can either be voltage (J2 ON) or current (J4 ON). With J1 OFF the Op Amp gives a gain of 1, and with J1 ON it gives a gain of 2.
With J4 ON, the second Op Amp provides current feedback for the first Op Amp. It acts as a differential amplifier, using the 100R resistor as a current sensing element. The 47R resistor does nothing except fix a linearity problem the circuit had at low outputs. Two 10k resistors were used in series because 20k was not available.
The jumper settings indicate how to select the desired voltage and current ranges. Hope the ideas in this circuit are helpful to you all.
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<A HREF="http://www.piclist.com/Techref/microchip/aout.htm"> Analog Output with jumper settings for voltage and current ranges</A>
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