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For an application we need a DC voltage reducer that works as follows:
Outgoing voltage = always Ingoing voltage constant minus 1V.
The DC range is 0 – 2V.
We have 8 ports and separate for each port we need it.
Best, Eric Preiss | Applications and Validation Engineer | Linear and Low Dropout Regulators | Texas Instruments
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In reply to Eric.Preiss:
Vout = Vin-1V -> ok
DC range 0-2V is for Vin
Yes, Vout has to go to negative voltage (max -1V).
Current: application is pH-measurement via impedance-transducer
Output current is very less. I approximate 40 - 200mA
In reply to Erwin Schott:
It sounds like a difference amplifier would work for your application my only concern is that the input impedance of the difference amplifier may effect the performance of the impedance transducer. I'm not familiar with an impedance transducer, can you provide a datasheet of the impedance transducer?
Why do you need to subtract only 1V off of the input?
An instrumentation amplifier such as the INA116 can provide a very accurate design for pH sensors. Have you considered this approach?
In reply to Tim Claycomb:
How about the circuit below? It converts 0-2V into 0-1V and has an input impedance of 1.5MOhms. It was difficult to understand from your requirement but it seems like the circuit goals are to attenuate a 2V signal into a 1V signal, not necessarily just to subtract 1V from the input.
Regards,Collin WellsPrecision ADC Applications
In reply to Collin Wells:
In my reply to Timothy Claycomb I wrote Vout = max. +1V. Sorry I forgot the minus-sign. Vout must be plus/minus 1V.
The measurement range of an pH-electrode is plus/minus 0,5V.
So the voltage is not to be sufficient to reduce from 2 to 1V but if a modified above circuit will convert it to minus would be nice.
For example please see the diagram
Index A stands for Ausgang = Out and E for Elektrode = Electrode
In the example 0-20 mA gives via 12,4 Ohm an output 0-248mV. What we need in that case is an output plus/minus 470mV. So the 0-248mV output has to convert to minus/plus.
But for generally purpose we prefer an output extended range plus/minus 1V for an input 0 to 2V.
For an output voltage of +/-1V you will need to use dual supplies, for example +/-15V. You mentioned you have a +24V supply available but do you also have a negative supply rail available? If so, what is the negative supply voltage you have available?
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