On 07/17/2014 10:26 AM, Randy Evans wrote: > Frank, > > The high cost is my concern, although high performance demands high price > typically. I am trying to double the voltage reference from either an > LM399 or LTZ1000, hence the need for precision matched resistors for a x2 > non-inverting amplifier (using a LT1151 precision op amp). An alternative > I am investigating is using the LTC1043 in a voltage doubling circuit as > shown in Linear Technology app note AN 42, page 6, Figure 16. It states > that Vout = 2xVin +/- 5 ppm. I am less concerned about the absolute > accuracy than I am about the long term stability. I assume that a high > quality capacitor is required (low leakage, low ESR, low dielectric > absorbtion, etc.) but the circuit does not appear to be dependent on the > absolute value of the capacitors. I'm not sure if the two 1uF caps need > to be matched. If they do then that would be a show stopper. > > Does anyone have any experience using the LTC1043 in such a circuit?
Hi Randy, There are some other error sources that might need to be considered when using the LTC1043. I have not used the LTC1043, but note that on the data sheet there is a small charge injection at each of the switch pins. In the multiply by 2 circuit shown on the data sheet they are using 1 ufd caps. Typical charge injection (depends on voltage level) is 8 pC. With the 1 ufd caps this is 8 uV. I assume there is some offsetting effect - but this might be a significant contributor to the 5 ppm error that is mentioned. There is also a 6 nA (typical) leakage mentioned. During the "hold" time ( about 1 msec) of the output 1 ufd cap this comes to 6 uV. Regards, Bob Smither
<<attachment: smither.vcf>>
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