双极性控制数字放大器-Dual-Polarity Ampli

文章摘要：Figure 2. Using a digital potentiometer in place of S1 and S2 allows digital control of the gain of this circuit to be swept from -1 to +1. A feature of the DS1267 is that it powers up with the wiper in the center of the pot, resulting in equal levels being present at the inverting and noninverting

双极性控制数字放大器-Dual-Polarity Ampli,标签：计算机控制技术,工厂电气控制技术,http://www.88dzw.com


Figure 2. Using a digital potentiometer in place of S1 and S2 allows digital control of the gain of this circuit to be swept from -1 to +1. A feature of the DS1267 is that it powers up with the wiper in the center of the pot, resulting in equal levels being present at the inverting and noninverting inputs. This causes no output from the op amp, creating an effective power-on mute function.

Other Features

An added feature of this circuit is that when the DS1267 first powers up, the wiper is automatically set to the midpoint of the pot. This results in equal signals being sent to the op amp inputs, resulting in no signal from the op amp output - in effect, creating a power-on mute function!

Logarithmic potentiometers like the DS1802 may be used in this circuit configuration, but due to the logarithmic taper, do not realize a smooth transition from inverting to noninverting gains. Some gain control is possible, but it is not symmetric between the two operating modes. Still, just bouncing between the high and low ends of the pot accomplishes the switching action between gains of -1 and +1, so again an "extra" pot may be used in place of analog switches.

This is an updated version of a circuit which appeared in EDN Magazine's Design Ideas, September 12, 1996, pg. 184.

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