MCP6491 datasheet(19/50 Pages) MICROCHIP

No de pièce	MCP6491

Description	7.5 MHz, Low-Input Bias Current Op Amps

PDF	50 Pages

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Fabricant	MICROCHIP [Microchip Technology]

Site Internet	http://www.microchip.com

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 2012-2013 Microchip Technology Inc.

DS20002321C-page 19

MCP6491/2/4

4.7.3

PH ELECTRODE AMPLIFIER

The MCP6491/2/4 op amps can be used for sensing

applications where the sensor has high output

impedance, such as a pH electrode sensor; its output

impedance is in the range of 1 M

 to 1G. The key op

amp specifications for these kinds of applications are

low-input bias current and high-input impedance.

A typical sensing circuit is shown in Figure 4-12, it is

implemented with a non-inverting amplifier which has a

gain of 1+R2/R1. The input voltage error due to input

bias current is equal to IB*ROUT, which is amplified by

1+R2/R1 at the output. To minimize the voltage error

and get the VOUT with better accuracy, the IB must be

small enough.

FIGURE 4-12:

pH Electrode Amplifier.

VOUT

VIN

–

MCP6491

pH electrode

VSEN

VSEN is the sensed voltage by pH electrode

ROUT is the pH electrode’s output impedance

–

ROUT

MCP6491 Fiches technique(PDF) 19 Page - Microchip Technology