In a previous article, Design a Bipolar to Unipolar Converter to Drive an ADC, I presented a method for designing a bipolar to unipolar converter using a summing amplifier. In this article I am going to show more examples of bipolar to unipolar converters which are based on a summing amplifier configuration. You can adapt them to your needs if you use the method I described in the previous article.
Input -1V to +1V, Output 0V to +5V, Reference voltage +5V
Figure 1
Input -2V to +2V, Output 0V to +5V, Reference voltage +5V
Figure 2
Input -3V to +3V, Output 0V to +5V, Reference voltage +5V
Figure 3
Input -10V to +10V, Output 0V to +5V, Reference voltage +2.5V
Figure 4
Input -5V to +5V, Output 0V to +5V, Reference voltage +2.5V
Figure 5
Input -1V to +1V, Output 0V to +5V, Reference voltage +2.5V
Figure 6
Related Articles
- Design a Bipolar to Unipolar Converter with a 3-input Summing Amplifier Since the publication of Design a Bipolar to Unipolar Converter to Drive an ADC, several readers contacted me with requests...
- Design a Unipolar to Bipolar Converter for a Unipolar Voltage Output DAC Unipolar to bipolar converters are useful when we have to have a unipolar component to do a certain job in...
- Design a Bipolar to Unipolar Converter to Drive an ADC Most ADCs have a unipolar input range that can be a problem when designing bipolar circuits. Some common ADC input...
Related articles by YARP.
Tags: bipolar, converter, op amp, operational amplifier, Summing Amplifier, summing amplifier examples, unipolar
Categories: Analog Design, Electronic Circuits Examples, Summing Amplifier
Categories: Analog Design, Electronic Circuits Examples, Summing Amplifier
Hi,
reading your previous articles on this topic I came up with pretty much the same resistors for the problem shown in figure 4. What I was wondering about is the stability of this circuit. Since the gain v_out/vin is below one, do I have to be careful when choosing the op amp? If I recall correctly there is a pretty good chance of picking the wrong op amp and ending up with an oscillator.
Btw, thanks for this great site!
khor, you’re welcome and thanks for visiting.
As for your question, yes, one needs to choose the op amp carefully. Op amp manufacturers show in their datasheets the gain and phase bode plots as well as the phase margin versus frequency. Typically, if you choose a unity gain stable op amp it has less chances to oscillate below unity gain. However, as manufacturers try to boost the gain as much as possible, due to competition, the op amp internal compensation may be just about right to make sure the phase margin is above 45 degrees all the way down to 0 dB gain. Below 0 dB gain, one might see an extra pole and that means trouble. Therefore, since there are many op amps out there and the designer circuit might have a capacitor that reduces the bandwidth even more, I can only advise to always check the manufacturer datasheet and the phase margin plot for that particular op amp of choice.
how bipolar voltages can be converted to unipolar voltages using a summing operational amplifier
If you want to understand how I designed the examples in this article read this: Design a Bipolar to Unipolar Converter to Drive an ADC . In that article I use a summing amplifier, and I explain step-by-step how to calculate the resistors.