| ??? 10/18/07 19:14 Read: times |
#145912 - Difference Amplifier Responding to: ???'s previous message |
If you don't want to use a chip designed specifically for the purpose, you need some technique of measuring a differential voltage. You could use an Instrumentation Amplifier(IA) or make one from 2 or 3 op-amps. There are issues on common mode rejection that are a function of the matching of the resistors and so a commercial IA is normally better. A second option is a Difference Amplifier. It has the problem that there are unequal input impedances on either side of the sense resistor. If you can live with that, the advantages are 1) it only requires a single op-amp and 2) because it uses a resitive divider you can move the input voltage to the op-amp to below the supply rail.
You can see some variations on this in the NS app note http://www.national.com/an/AN/AN-31.pdf -Aubrey |
| Topic | Author | Date |
| OT: Opamp Bidirectional Current Sense | 01/01/70 00:00 | |
| A schematic would heavily help clear things | 01/01/70 00:00 | |
| High-Side | 01/01/70 00:00 | |
| WHY? | 01/01/70 00:00 | |
| where? | 01/01/70 00:00 | |
| Answers | 01/01/70 00:00 | |
| then add another in the minus line | 01/01/70 00:00 | |
| Difference Amplifier | 01/01/70 00:00 | |
Another solution | 01/01/70 00:00 |